JSONArray.java

package org.json;

/*
 Copyright (c) 2002 JSON.org

 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in all
 copies or substantial portions of the Software.

 The Software shall be used for Good, not Evil.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
 */

import java.io.IOException;
import java.io.StringWriter;
import java.io.Writer;
import java.lang.reflect.Array;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map;


/**
 * A JSONArray is an ordered sequence of values. Its external text form is a
 * string wrapped in square brackets with commas separating the values. The
 * internal form is an object having <code>get</code> and <code>opt</code>
 * methods for accessing the values by index, and <code>put</code> methods for
 * adding or replacing values. The values can be any of these types:
 * <code>Boolean</code>, <code>JSONArray</code>, <code>JSONObject</code>,
 * <code>Number</code>, <code>String</code>, or the
 * <code>JSONObject.NULL object</code>.
 * <p>
 * The constructor can convert a JSON text into a Java object. The
 * <code>toString</code> method converts to JSON text.
 * <p>
 * A <code>get</code> method returns a value if one can be found, and throws an
 * exception if one cannot be found. An <code>opt</code> method returns a
 * default value instead of throwing an exception, and so is useful for
 * obtaining optional values.
 * <p>
 * The generic <code>get()</code> and <code>opt()</code> methods return an
 * object which you can cast or query for type. There are also typed
 * <code>get</code> and <code>opt</code> methods that do type checking and type
 * coercion for you.
 * <p>
 * The texts produced by the <code>toString</code> methods strictly conform to
 * JSON syntax rules. The constructors are more forgiving in the texts they will
 * accept:
 * <ul>
 * <li>An extra <code>,</code>&nbsp;<small>(comma)</small> may appear just
 * before the closing bracket.</li>
 * <li>The <code>null</code> value will be inserted when there is <code>,</code>
 * &nbsp;<small>(comma)</small> elision.</li>
 * <li>Strings may be quoted with <code>'</code>&nbsp;<small>(single
 * quote)</small>.</li>
 * <li>Strings do not need to be quoted at all if they do not begin with a quote
 * or single quote, and if they do not contain leading or trailing spaces, and
 * if they do not contain any of these characters:
 * <code>{ } [ ] / \ : , #</code> and if they do not look like numbers and
 * if they are not the reserved words <code>true</code>, <code>false</code>, or
 * <code>null</code>.</li>
 * </ul>
 *
 * @author JSON.org
 * @version 2016-08/15
 */
public class JSONArray implements Iterable<Object> {

    /**
     * The arrayList where the JSONArray's properties are kept.
     */
    private final ArrayList<Object> myArrayList;

    /**
     * Construct an empty JSONArray.
     */
    public JSONArray() {
        this.myArrayList = new ArrayList<Object>();
    }

    /**
     * Construct a JSONArray from a JSONTokener.
     *
     * @param x
     *            A JSONTokener
     * @throws JSONException
     *             If there is a syntax error.
     */
    public JSONArray(JSONTokener x) throws JSONException {
        this();
        if (x.nextClean() != '[') {
            throw x.syntaxError("A JSONArray text must start with '['");
        }
        
        char nextChar = x.nextClean();
        if (nextChar == 0) {
            // array is unclosed. No ']' found, instead EOF
            throw x.syntaxError("Expected a ',' or ']'");
        }
        if (nextChar != ']') {
            x.back();
            for (;;) {
                if (x.nextClean() == ',') {
                    x.back();
                    this.myArrayList.add(JSONObject.NULL);
                } else {
                    x.back();
                    this.myArrayList.add(x.nextValue());
                }
                switch (x.nextClean()) {
                case 0:
                    // array is unclosed. No ']' found, instead EOF
                    throw x.syntaxError("Expected a ',' or ']'");
                case ',':
                    nextChar = x.nextClean();
                    if (nextChar == 0) {
                        // array is unclosed. No ']' found, instead EOF
                        throw x.syntaxError("Expected a ',' or ']'");
                    }
                    if (nextChar == ']') {
                        return;
                    }
                    x.back();
                    break;
                case ']':
                    return;
                default:
                    throw x.syntaxError("Expected a ',' or ']'");
                }
            }
        }
    }

    /**
     * Construct a JSONArray from a source JSON text.
     *
     * @param source
     *            A string that begins with <code>[</code>&nbsp;<small>(left
     *            bracket)</small> and ends with <code>]</code>
     *            &nbsp;<small>(right bracket)</small>.
     * @throws JSONException
     *             If there is a syntax error.
     */
    public JSONArray(String source) throws JSONException {
        this(new JSONTokener(source));
    }

    /**
     * Construct a JSONArray from a Collection.
     *
     * @param collection
     *            A Collection.
     */
    public JSONArray(Collection<?> collection) {
        if (collection == null) {
            this.myArrayList = new ArrayList<Object>();
        } else {
            this.myArrayList = new ArrayList<Object>(collection.size());
        	for (Object o: collection){
        		this.myArrayList.add(JSONObject.wrap(o));
        	}
        }
    }

    /**
     * Construct a JSONArray from an array.
     *
     * @param array
     *            Array. If the parameter passed is null, or not an array, an
     *            exception will be thrown.
     *
     * @throws JSONException
     *            If not an array or if an array value is non-finite number.
     * @throws NullPointerException
     *            Thrown if the array parameter is null.
     */
    public JSONArray(Object array) throws JSONException {
        this();
        if (array.getClass().isArray()) {
            int length = Array.getLength(array);
            this.myArrayList.ensureCapacity(length);
            for (int i = 0; i < length; i += 1) {
                this.put(JSONObject.wrap(Array.get(array, i)));
            }
        } else {
            throw new JSONException(
                    "JSONArray initial value should be a string or collection or array.");
        }
    }

    /**
     * Construct a JSONArray with the specified initial capacity.
     *
     * @param initialCapacity
     *            the initial capacity of the JSONArray.
     * @throws JSONException
     *             If the initial capacity is negative.
     */
    public JSONArray(int initialCapacity) throws JSONException {
    	if (initialCapacity < 0) {
            throw new JSONException(
                    "JSONArray initial capacity cannot be negative.");
    	}
    	this.myArrayList = new ArrayList<Object>(initialCapacity);
    }

    @Override
    public Iterator<Object> iterator() {
        return this.myArrayList.iterator();
    }

    /**
     * Get the object value associated with an index.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return An object value.
     * @throws JSONException
     *             If there is no value for the index.
     */
    public Object get(int index) throws JSONException {
        Object object = this.opt(index);
        if (object == null) {
            throw new JSONException("JSONArray[" + index + "] not found.");
        }
        return object;
    }

    /**
     * Get the boolean value associated with an index. The string values "true"
     * and "false" are converted to boolean.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return The truth.
     * @throws JSONException
     *             If there is no value for the index or if the value is not
     *             convertible to boolean.
     */
    public boolean getBoolean(int index) throws JSONException {
        Object object = this.get(index);
        if (object.equals(Boolean.FALSE)
                || (object instanceof String && ((String) object)
                        .equalsIgnoreCase("false"))) {
            return false;
        } else if (object.equals(Boolean.TRUE)
                || (object instanceof String && ((String) object)
                        .equalsIgnoreCase("true"))) {
            return true;
        }
        throw wrongValueFormatException(index, "boolean", null);
    }

    /**
     * Get the double value associated with an index.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return The value.
     * @throws JSONException
     *             If the key is not found or if the value cannot be converted
     *             to a number.
     */
    public double getDouble(int index) throws JSONException {
        final Object object = this.get(index);
        if(object instanceof Number) {
            return ((Number)object).doubleValue();
        }
        try {
            return Double.parseDouble(object.toString());
        } catch (Exception e) {
            throw wrongValueFormatException(index, "double", e);
        }
    }

    /**
     * Get the float value associated with a key.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return The numeric value.
     * @throws JSONException
     *             if the key is not found or if the value is not a Number
     *             object and cannot be converted to a number.
     */
    public float getFloat(int index) throws JSONException {
        final Object object = this.get(index);
        if(object instanceof Number) {
            return ((Float)object).floatValue();
        }
        try {
            return Float.parseFloat(object.toString());
        } catch (Exception e) {
            throw wrongValueFormatException(index, "float", e);
        }
    }

    /**
     * Get the Number value associated with a key.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return The numeric value.
     * @throws JSONException
     *             if the key is not found or if the value is not a Number
     *             object and cannot be converted to a number.
     */
    public Number getNumber(int index) throws JSONException {
        Object object = this.get(index);
        try {
            if (object instanceof Number) {
                return (Number)object;
            }
            return JSONObject.stringToNumber(object.toString());
        } catch (Exception e) {
            throw wrongValueFormatException(index, "number", e);
        }
    }

    /**
     * Get the enum value associated with an index.
     * 
     * @param <E>
     *            Enum Type
     * @param clazz
     *            The type of enum to retrieve.
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return The enum value at the index location
     * @throws JSONException
     *            if the key is not found or if the value cannot be converted
     *            to an enum.
     */
    public <E extends Enum<E>> E getEnum(Class<E> clazz, int index) throws JSONException {
        E val = optEnum(clazz, index);
        if(val==null) {
            // JSONException should really take a throwable argument.
            // If it did, I would re-implement this with the Enum.valueOf
            // method and place any thrown exception in the JSONException
            throw wrongValueFormatException(index, "enum of type "
                    + JSONObject.quote(clazz.getSimpleName()), null);
        }
        return val;
    }

    /**
     * Get the BigDecimal value associated with an index. If the value is float
     * or double, the the {@link BigDecimal#BigDecimal(double)} constructor
     * will be used. See notes on the constructor for conversion issues that
     * may arise.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return The value.
     * @throws JSONException
     *             If the key is not found or if the value cannot be converted
     *             to a BigDecimal.
     */
    public BigDecimal getBigDecimal (int index) throws JSONException {
        Object object = this.get(index);
        BigDecimal val = JSONObject.objectToBigDecimal(object, null);
        if(val == null) {
            throw wrongValueFormatException(index, "BigDecimal", object, null);
        }
        return val;
    }

    /**
     * Get the BigInteger value associated with an index.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return The value.
     * @throws JSONException
     *             If the key is not found or if the value cannot be converted
     *             to a BigInteger.
     */
    public BigInteger getBigInteger (int index) throws JSONException {
        Object object = this.get(index);
        BigInteger val = JSONObject.objectToBigInteger(object, null);
        if(val == null) {
            throw wrongValueFormatException(index, "BigInteger", object, null);
        }
        return val;
    }

    /**
     * Get the int value associated with an index.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return The value.
     * @throws JSONException
     *             If the key is not found or if the value is not a number.
     */
    public int getInt(int index) throws JSONException {
        final Object object = this.get(index);
        if(object instanceof Number) {
            return ((Number)object).intValue();
        }
        try {
            return Integer.parseInt(object.toString());
        } catch (Exception e) {
            throw wrongValueFormatException(index, "int", e);
        }
    }

    /**
     * Get the JSONArray associated with an index.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return A JSONArray value.
     * @throws JSONException
     *             If there is no value for the index. or if the value is not a
     *             JSONArray
     */
    public JSONArray getJSONArray(int index) throws JSONException {
        Object object = this.get(index);
        if (object instanceof JSONArray) {
            return (JSONArray) object;
        }
        throw wrongValueFormatException(index, "JSONArray", null);
    }

    /**
     * Get the JSONObject associated with an index.
     *
     * @param index
     *            subscript
     * @return A JSONObject value.
     * @throws JSONException
     *             If there is no value for the index or if the value is not a
     *             JSONObject
     */
    public JSONObject getJSONObject(int index) throws JSONException {
        Object object = this.get(index);
        if (object instanceof JSONObject) {
            return (JSONObject) object;
        }
        throw wrongValueFormatException(index, "JSONObject", null);
    }

    /**
     * Get the long value associated with an index.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return The value.
     * @throws JSONException
     *             If the key is not found or if the value cannot be converted
     *             to a number.
     */
    public long getLong(int index) throws JSONException {
        final Object object = this.get(index);
        if(object instanceof Number) {
            return ((Number)object).longValue();
        }
        try {
            return Long.parseLong(object.toString());
        } catch (Exception e) {
            throw wrongValueFormatException(index, "long", e);
        }
    }

    /**
     * Get the string associated with an index.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return A string value.
     * @throws JSONException
     *             If there is no string value for the index.
     */
    public String getString(int index) throws JSONException {
        Object object = this.get(index);
        if (object instanceof String) {
            return (String) object;
        }
        throw wrongValueFormatException(index, "String", null);
    }

    /**
     * Determine if the value is <code>null</code>.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return true if the value at the index is <code>null</code>, or if there is no value.
     */
    public boolean isNull(int index) {
        return JSONObject.NULL.equals(this.opt(index));
    }

    /**
     * Make a string from the contents of this JSONArray. The
     * <code>separator</code> string is inserted between each element. Warning:
     * This method assumes that the data structure is acyclical.
     *
     * @param separator
     *            A string that will be inserted between the elements.
     * @return a string.
     * @throws JSONException
     *             If the array contains an invalid number.
     */
    public String join(String separator) throws JSONException {
        int len = this.length();
        if (len == 0) {
            return "";
        }
        
        StringBuilder sb = new StringBuilder(
                   JSONObject.valueToString(this.myArrayList.get(0)));

        for (int i = 1; i < len; i++) {
            sb.append(separator)
              .append(JSONObject.valueToString(this.myArrayList.get(i)));
        }
        return sb.toString();
    }

    /**
     * Get the number of elements in the JSONArray, included nulls.
     *
     * @return The length (or size).
     */
    public int length() {
        return this.myArrayList.size();
    }

    /**
     * Get the optional object value associated with an index.
     *
     * @param index
     *            The index must be between 0 and length() - 1. If not, null is returned.
     * @return An object value, or null if there is no object at that index.
     */
    public Object opt(int index) {
        return (index < 0 || index >= this.length()) ? null : this.myArrayList
                .get(index);
    }

    /**
     * Get the optional boolean value associated with an index. It returns false
     * if there is no value at that index, or if the value is not Boolean.TRUE
     * or the String "true".
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return The truth.
     */
    public boolean optBoolean(int index) {
        return this.optBoolean(index, false);
    }

    /**
     * Get the optional boolean value associated with an index. It returns the
     * defaultValue if there is no value at that index or if it is not a Boolean
     * or the String "true" or "false" (case insensitive).
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @param defaultValue
     *            A boolean default.
     * @return The truth.
     */
    public boolean optBoolean(int index, boolean defaultValue) {
        try {
            return this.getBoolean(index);
        } catch (Exception e) {
            return defaultValue;
        }
    }

    /**
     * Get the optional double value associated with an index. NaN is returned
     * if there is no value for the index, or if the value is not a number and
     * cannot be converted to a number.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return The value.
     */
    public double optDouble(int index) {
        return this.optDouble(index, Double.NaN);
    }

    /**
     * Get the optional double value associated with an index. The defaultValue
     * is returned if there is no value for the index, or if the value is not a
     * number and cannot be converted to a number.
     *
     * @param index
     *            subscript
     * @param defaultValue
     *            The default value.
     * @return The value.
     */
    public double optDouble(int index, double defaultValue) {
        final Number val = this.optNumber(index, null);
        if (val == null) {
            return defaultValue;
        }
        final double doubleValue = val.doubleValue();
        // if (Double.isNaN(doubleValue) || Double.isInfinite(doubleValue)) {
        // return defaultValue;
        // }
        return doubleValue;
    }

    /**
     * Get the optional float value associated with an index. NaN is returned
     * if there is no value for the index, or if the value is not a number and
     * cannot be converted to a number.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return The value.
     */
    public float optFloat(int index) {
        return this.optFloat(index, Float.NaN);
    }

    /**
     * Get the optional float value associated with an index. The defaultValue
     * is returned if there is no value for the index, or if the value is not a
     * number and cannot be converted to a number.
     *
     * @param index
     *            subscript
     * @param defaultValue
     *            The default value.
     * @return The value.
     */
    public float optFloat(int index, float defaultValue) {
        final Number val = this.optNumber(index, null);
        if (val == null) {
            return defaultValue;
        }
        final float floatValue = val.floatValue();
        // if (Float.isNaN(floatValue) || Float.isInfinite(floatValue)) {
        // return floatValue;
        // }
        return floatValue;
    }

    /**
     * Get the optional int value associated with an index. Zero is returned if
     * there is no value for the index, or if the value is not a number and
     * cannot be converted to a number.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return The value.
     */
    public int optInt(int index) {
        return this.optInt(index, 0);
    }

    /**
     * Get the optional int value associated with an index. The defaultValue is
     * returned if there is no value for the index, or if the value is not a
     * number and cannot be converted to a number.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @param defaultValue
     *            The default value.
     * @return The value.
     */
    public int optInt(int index, int defaultValue) {
        final Number val = this.optNumber(index, null);
        if (val == null) {
            return defaultValue;
        }
        return val.intValue();
    }

    /**
     * Get the enum value associated with a key.
     * 
     * @param <E>
     *            Enum Type
     * @param clazz
     *            The type of enum to retrieve.
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return The enum value at the index location or null if not found
     */
    public <E extends Enum<E>> E optEnum(Class<E> clazz, int index) {
        return this.optEnum(clazz, index, null);
    }

    /**
     * Get the enum value associated with a key.
     * 
     * @param <E>
     *            Enum Type
     * @param clazz
     *            The type of enum to retrieve.
     * @param index
     *            The index must be between 0 and length() - 1.
     * @param defaultValue
     *            The default in case the value is not found
     * @return The enum value at the index location or defaultValue if
     *            the value is not found or cannot be assigned to clazz
     */
    public <E extends Enum<E>> E optEnum(Class<E> clazz, int index, E defaultValue) {
        try {
            Object val = this.opt(index);
            if (JSONObject.NULL.equals(val)) {
                return defaultValue;
            }
            if (clazz.isAssignableFrom(val.getClass())) {
                // we just checked it!
                @SuppressWarnings("unchecked")
                E myE = (E) val;
                return myE;
            }
            return Enum.valueOf(clazz, val.toString());
        } catch (IllegalArgumentException e) {
            return defaultValue;
        } catch (NullPointerException e) {
            return defaultValue;
        }
    }

    /**
     * Get the optional BigInteger value associated with an index. The 
     * defaultValue is returned if there is no value for the index, or if the 
     * value is not a number and cannot be converted to a number.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @param defaultValue
     *            The default value.
     * @return The value.
     */
    public BigInteger optBigInteger(int index, BigInteger defaultValue) {
        Object val = this.opt(index);
        return JSONObject.objectToBigInteger(val, defaultValue);
    }

    /**
     * Get the optional BigDecimal value associated with an index. The 
     * defaultValue is returned if there is no value for the index, or if the 
     * value is not a number and cannot be converted to a number. If the value
     * is float or double, the the {@link BigDecimal#BigDecimal(double)}
     * constructor will be used. See notes on the constructor for conversion
     * issues that may arise.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @param defaultValue
     *            The default value.
     * @return The value.
     */
    public BigDecimal optBigDecimal(int index, BigDecimal defaultValue) {
        Object val = this.opt(index);
        return JSONObject.objectToBigDecimal(val, defaultValue);
    }

    /**
     * Get the optional JSONArray associated with an index.
     *
     * @param index
     *            subscript
     * @return A JSONArray value, or null if the index has no value, or if the
     *         value is not a JSONArray.
     */
    public JSONArray optJSONArray(int index) {
        Object o = this.opt(index);
        return o instanceof JSONArray ? (JSONArray) o : null;
    }

    /**
     * Get the optional JSONObject associated with an index. Null is returned if
     * the key is not found, or null if the index has no value, or if the value
     * is not a JSONObject.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return A JSONObject value.
     */
    public JSONObject optJSONObject(int index) {
        Object o = this.opt(index);
        return o instanceof JSONObject ? (JSONObject) o : null;
    }

    /**
     * Get the optional long value associated with an index. Zero is returned if
     * there is no value for the index, or if the value is not a number and
     * cannot be converted to a number.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return The value.
     */
    public long optLong(int index) {
        return this.optLong(index, 0);
    }

    /**
     * Get the optional long value associated with an index. The defaultValue is
     * returned if there is no value for the index, or if the value is not a
     * number and cannot be converted to a number.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @param defaultValue
     *            The default value.
     * @return The value.
     */
    public long optLong(int index, long defaultValue) {
        final Number val = this.optNumber(index, null);
        if (val == null) {
            return defaultValue;
        }
        return val.longValue();
    }

    /**
     * Get an optional {@link Number} value associated with a key, or <code>null</code>
     * if there is no such key or if the value is not a number. If the value is a string,
     * an attempt will be made to evaluate it as a number ({@link BigDecimal}). This method
     * would be used in cases where type coercion of the number value is unwanted.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return An object which is the value.
     */
    public Number optNumber(int index) {
        return this.optNumber(index, null);
    }

    /**
     * Get an optional {@link Number} value associated with a key, or the default if there
     * is no such key or if the value is not a number. If the value is a string,
     * an attempt will be made to evaluate it as a number ({@link BigDecimal}). This method
     * would be used in cases where type coercion of the number value is unwanted.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @param defaultValue
     *            The default.
     * @return An object which is the value.
     */
    public Number optNumber(int index, Number defaultValue) {
        Object val = this.opt(index);
        if (JSONObject.NULL.equals(val)) {
            return defaultValue;
        }
        if (val instanceof Number){
            return (Number) val;
        }
        
        if (val instanceof String) {
            try {
                return JSONObject.stringToNumber((String) val);
            } catch (Exception e) {
                return defaultValue;
            }
        }
        return defaultValue;
    }

    /**
     * Get the optional string value associated with an index. It returns an
     * empty string if there is no value at that index. If the value is not a
     * string and is not null, then it is converted to a string.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @return A String value.
     */
    public String optString(int index) {
        return this.optString(index, "");
    }

    /**
     * Get the optional string associated with an index. The defaultValue is
     * returned if the key is not found.
     *
     * @param index
     *            The index must be between 0 and length() - 1.
     * @param defaultValue
     *            The default value.
     * @return A String value.
     */
    public String optString(int index, String defaultValue) {
        Object object = this.opt(index);
        return JSONObject.NULL.equals(object) ? defaultValue : object
                .toString();
    }

    /**
     * Append a boolean value. This increases the array's length by one.
     *
     * @param value
     *            A boolean value.
     * @return this.
     */
    public JSONArray put(boolean value) {
        return this.put(value ? Boolean.TRUE : Boolean.FALSE);
    }

    /**
     * Put a value in the JSONArray, where the value will be a JSONArray which
     * is produced from a Collection.
     *
     * @param value
     *            A Collection value.
     * @return this.
     * @throws JSONException
     *            If the value is non-finite number.
     */
    public JSONArray put(Collection<?> value) {
        return this.put(new JSONArray(value));
    }

    /**
     * Append a double value. This increases the array's length by one.
     *
     * @param value
     *            A double value.
     * @return this.
     * @throws JSONException
     *             if the value is not finite.
     */
    public JSONArray put(double value) throws JSONException {
        return this.put(Double.valueOf(value));
    }
    
    /**
     * Append a float value. This increases the array's length by one.
     *
     * @param value
     *            A float value.
     * @return this.
     * @throws JSONException
     *             if the value is not finite.
     */
    public JSONArray put(float value) throws JSONException {
        return this.put(Float.valueOf(value));
    }

    /**
     * Append an int value. This increases the array's length by one.
     *
     * @param value
     *            An int value.
     * @return this.
     */
    public JSONArray put(int value) {
        return this.put(Integer.valueOf(value));
    }

    /**
     * Append an long value. This increases the array's length by one.
     *
     * @param value
     *            A long value.
     * @return this.
     */
    public JSONArray put(long value) {
        return this.put(Long.valueOf(value));
    }

    /**
     * Put a value in the JSONArray, where the value will be a JSONObject which
     * is produced from a Map.
     *
     * @param value
     *            A Map value.
     * @return this.
     * @throws JSONException
     *            If a value in the map is non-finite number.
     * @throws NullPointerException
     *            If a key in the map is <code>null</code>
     */
    public JSONArray put(Map<?, ?> value) {
        return this.put(new JSONObject(value));
    }

    /**
     * Append an object value. This increases the array's length by one.
     *
     * @param value
     *            An object value. The value should be a Boolean, Double,
     *            Integer, JSONArray, JSONObject, Long, or String, or the
     *            JSONObject.NULL object.
     * @return this.
     * @throws JSONException
     *            If the value is non-finite number.
     */
    public JSONArray put(Object value) {
        JSONObject.testValidity(value);
        this.myArrayList.add(value);
        return this;
    }

    /**
     * Put or replace a boolean value in the JSONArray. If the index is greater
     * than the length of the JSONArray, then null elements will be added as
     * necessary to pad it out.
     *
     * @param index
     *            The subscript.
     * @param value
     *            A boolean value.
     * @return this.
     * @throws JSONException
     *             If the index is negative.
     */
    public JSONArray put(int index, boolean value) throws JSONException {
        return this.put(index, value ? Boolean.TRUE : Boolean.FALSE);
    }

    /**
     * Put a value in the JSONArray, where the value will be a JSONArray which
     * is produced from a Collection.
     *
     * @param index
     *            The subscript.
     * @param value
     *            A Collection value.
     * @return this.
     * @throws JSONException
     *             If the index is negative or if the value is non-finite.
     */
    public JSONArray put(int index, Collection<?> value) throws JSONException {
        return this.put(index, new JSONArray(value));
    }

    /**
     * Put or replace a double value. If the index is greater than the length of
     * the JSONArray, then null elements will be added as necessary to pad it
     * out.
     *
     * @param index
     *            The subscript.
     * @param value
     *            A double value.
     * @return this.
     * @throws JSONException
     *             If the index is negative or if the value is non-finite.
     */
    public JSONArray put(int index, double value) throws JSONException {
        return this.put(index, Double.valueOf(value));
    }

    /**
     * Put or replace a float value. If the index is greater than the length of
     * the JSONArray, then null elements will be added as necessary to pad it
     * out.
     *
     * @param index
     *            The subscript.
     * @param value
     *            A float value.
     * @return this.
     * @throws JSONException
     *             If the index is negative or if the value is non-finite.
     */
    public JSONArray put(int index, float value) throws JSONException {
        return this.put(index, Float.valueOf(value));
    }

    /**
     * Put or replace an int value. If the index is greater than the length of
     * the JSONArray, then null elements will be added as necessary to pad it
     * out.
     *
     * @param index
     *            The subscript.
     * @param value
     *            An int value.
     * @return this.
     * @throws JSONException
     *             If the index is negative.
     */
    public JSONArray put(int index, int value) throws JSONException {
        return this.put(index, Integer.valueOf(value));
    }

    /**
     * Put or replace a long value. If the index is greater than the length of
     * the JSONArray, then null elements will be added as necessary to pad it
     * out.
     *
     * @param index
     *            The subscript.
     * @param value
     *            A long value.
     * @return this.
     * @throws JSONException
     *             If the index is negative.
     */
    public JSONArray put(int index, long value) throws JSONException {
        return this.put(index, Long.valueOf(value));
    }

    /**
     * Put a value in the JSONArray, where the value will be a JSONObject that
     * is produced from a Map.
     *
     * @param index
     *            The subscript.
     * @param value
     *            The Map value.
     * @return this.
     * @throws JSONException
     *             If the index is negative or if the the value is an invalid
     *             number.
     * @throws NullPointerException
     *             If a key in the map is <code>null</code>
     */
    public JSONArray put(int index, Map<?, ?> value) throws JSONException {
        this.put(index, new JSONObject(value));
        return this;
    }

    /**
     * Put or replace an object value in the JSONArray. If the index is greater
     * than the length of the JSONArray, then null elements will be added as
     * necessary to pad it out.
     *
     * @param index
     *            The subscript.
     * @param value
     *            The value to put into the array. The value should be a
     *            Boolean, Double, Integer, JSONArray, JSONObject, Long, or
     *            String, or the JSONObject.NULL object.
     * @return this.
     * @throws JSONException
     *             If the index is negative or if the the value is an invalid
     *             number.
     */
    public JSONArray put(int index, Object value) throws JSONException {
        if (index < 0) {
            throw new JSONException("JSONArray[" + index + "] not found.");
        }
        if (index < this.length()) {
            JSONObject.testValidity(value);
            this.myArrayList.set(index, value);
            return this;
        }
        if(index == this.length()){
            // simple append
            return this.put(value);
        }
        // if we are inserting past the length, we want to grow the array all at once
        // instead of incrementally.
        this.myArrayList.ensureCapacity(index + 1);
        while (index != this.length()) {
            // we don't need to test validity of NULL objects
            this.myArrayList.add(JSONObject.NULL);
        }
        return this.put(value);
    }
    
    /**
     * Creates a JSONPointer using an initialization string and tries to 
     * match it to an item within this JSONArray. For example, given a
     * JSONArray initialized with this document:
     * <pre>
     * [
     *     {"b":"c"}
     * ]
     * </pre>
     * and this JSONPointer string: 
     * <pre>
     * "/0/b"
     * </pre>
     * Then this method will return the String "c"
     * A JSONPointerException may be thrown from code called by this method.
     *
     * @param jsonPointer string that can be used to create a JSONPointer
     * @return the item matched by the JSONPointer, otherwise null
     */
    public Object query(String jsonPointer) {
        return query(new JSONPointer(jsonPointer));
    }
    
    /**
     * Uses a user initialized JSONPointer  and tries to 
     * match it to an item within this JSONArray. For example, given a
     * JSONArray initialized with this document:
     * <pre>
     * [
     *     {"b":"c"}
     * ]
     * </pre>
     * and this JSONPointer: 
     * <pre>
     * "/0/b"
     * </pre>
     * Then this method will return the String "c"
     * A JSONPointerException may be thrown from code called by this method.
     *
     * @param jsonPointer string that can be used to create a JSONPointer
     * @return the item matched by the JSONPointer, otherwise null
     */
    public Object query(JSONPointer jsonPointer) {
        return jsonPointer.queryFrom(this);
    }
    
    /**
     * Queries and returns a value from this object using {@code jsonPointer}, or
     * returns null if the query fails due to a missing key.
     * 
     * @param jsonPointer the string representation of the JSON pointer
     * @return the queried value or {@code null}
     * @throws IllegalArgumentException if {@code jsonPointer} has invalid syntax
     */
    public Object optQuery(String jsonPointer) {
    	return optQuery(new JSONPointer(jsonPointer));
    }
    
    /**
     * Queries and returns a value from this object using {@code jsonPointer}, or
     * returns null if the query fails due to a missing key.
     * 
     * @param jsonPointer The JSON pointer
     * @return the queried value or {@code null}
     * @throws IllegalArgumentException if {@code jsonPointer} has invalid syntax
     */
    public Object optQuery(JSONPointer jsonPointer) {
        try {
            return jsonPointer.queryFrom(this);
        } catch (JSONPointerException e) {
            return null;
        }
    }

    /**
     * Remove an index and close the hole.
     *
     * @param index
     *            The index of the element to be removed.
     * @return The value that was associated with the index, or null if there
     *         was no value.
     */
    public Object remove(int index) {
        return index >= 0 && index < this.length()
            ? this.myArrayList.remove(index)
            : null;
    }

    /**
     * Determine if two JSONArrays are similar.
     * They must contain similar sequences.
     *
     * @param other The other JSONArray
     * @return true if they are equal
     */
    public boolean similar(Object other) {
        if (!(other instanceof JSONArray)) {
            return false;
        }
        int len = this.length();
        if (len != ((JSONArray)other).length()) {
            return false;
        }
        for (int i = 0; i < len; i += 1) {
            Object valueThis = this.myArrayList.get(i);
            Object valueOther = ((JSONArray)other).myArrayList.get(i);
            if(valueThis == valueOther) {
            	continue;
            }
            if(valueThis == null) {
            	return false;
            }
            if (valueThis instanceof JSONObject) {
                if (!((JSONObject)valueThis).similar(valueOther)) {
                    return false;
                }
            } else if (valueThis instanceof JSONArray) {
                if (!((JSONArray)valueThis).similar(valueOther)) {
                    return false;
                }
            } else if (!valueThis.equals(valueOther)) {
                return false;
            }
        }
        return true;
    }

    /**
     * Produce a JSONObject by combining a JSONArray of names with the values of
     * this JSONArray.
     *
     * @param names
     *            A JSONArray containing a list of key strings. These will be
     *            paired with the values.
     * @return A JSONObject, or null if there are no names or if this JSONArray
     *         has no values.
     * @throws JSONException
     *             If any of the names are null.
     */
    public JSONObject toJSONObject(JSONArray names) throws JSONException {
        if (names == null || names.isEmpty() || this.isEmpty()) {
            return null;
        }
        JSONObject jo = new JSONObject(names.length());
        for (int i = 0; i < names.length(); i += 1) {
            jo.put(names.getString(i), this.opt(i));
        }
        return jo;
    }

    /**
     * Make a JSON text of this JSONArray. For compactness, no unnecessary
     * whitespace is added. If it is not possible to produce a syntactically
     * correct JSON text then null will be returned instead. This could occur if
     * the array contains an invalid number.
     * <p><b>
     * Warning: This method assumes that the data structure is acyclical.
     * </b>
     *
     * @return a printable, displayable, transmittable representation of the
     *         array.
     */
    @Override
    public String toString() {
        try {
            return this.toString(0);
        } catch (Exception e) {
            return null;
        }
    }

    /**
     * Make a pretty-printed JSON text of this JSONArray.
     * 
     * <p>If <pre> {@code indentFactor > 0}</pre> and the {@link JSONArray} has only
     * one element, then the array will be output on a single line:
     * <pre>{@code [1]}</pre>
     * 
     * <p>If an array has 2 or more elements, then it will be output across
     * multiple lines: <pre>{@code
     * [
     * 1,
     * "value 2",
     * 3
     * ]
     * }</pre>
     * <p><b>
     * Warning: This method assumes that the data structure is acyclical.
     * </b>
     * 
     * @param indentFactor
     *            The number of spaces to add to each level of indentation.
     * @return a printable, displayable, transmittable representation of the
     *         object, beginning with <code>[</code>&nbsp;<small>(left
     *         bracket)</small> and ending with <code>]</code>
     *         &nbsp;<small>(right bracket)</small>.
     * @throws JSONException if a called function fails
     */
    public String toString(int indentFactor) throws JSONException {
        StringWriter sw = new StringWriter();
        synchronized (sw.getBuffer()) {
            return this.write(sw, indentFactor, 0).toString();
        }
    }

    /**
     * Write the contents of the JSONArray as JSON text to a writer. For
     * compactness, no whitespace is added.
     * <p><b>
     * Warning: This method assumes that the data structure is acyclical.
     *</b>
     * @param writer the writer object
     * @return The writer.
     * @throws JSONException if a called function fails
     */
    public Writer write(Writer writer) throws JSONException {
        return this.write(writer, 0, 0);
    }

    /**
     * Write the contents of the JSONArray as JSON text to a writer.
     * 
     * <p>If <pre>{@code indentFactor > 0}</pre> and the {@link JSONArray} has only
     * one element, then the array will be output on a single line:
     * <pre>{@code [1]}</pre>
     * 
     * <p>If an array has 2 or more elements, then it will be output across
     * multiple lines: <pre>{@code
     * [
     * 1,
     * "value 2",
     * 3
     * ]
     * }</pre>
     * <p><b>
     * Warning: This method assumes that the data structure is acyclical.
     * </b>
     *
     * @param writer
     *            Writes the serialized JSON
     * @param indentFactor
     *            The number of spaces to add to each level of indentation.
     * @param indent
     *            The indentation of the top level.
     * @return The writer.
     * @throws JSONException if a called function fails or unable to write
     */
    public Writer write(Writer writer, int indentFactor, int indent)
            throws JSONException {
        try {
            boolean needsComma = false;
            int length = this.length();
            writer.write('[');

            if (length == 1) {
                try {
                    JSONObject.writeValue(writer, this.myArrayList.get(0),
                            indentFactor, indent);
                } catch (Exception e) {
                    throw new JSONException("Unable to write JSONArray value at index: 0", e);
                }
            } else if (length != 0) {
                final int newIndent = indent + indentFactor;

                for (int i = 0; i < length; i += 1) {
                    if (needsComma) {
                        writer.write(',');
                    }
                    if (indentFactor > 0) {
                        writer.write('\n');
                    }
                    JSONObject.indent(writer, newIndent);
                    try {
                        JSONObject.writeValue(writer, this.myArrayList.get(i),
                                indentFactor, newIndent);
                    } catch (Exception e) {
                        throw new JSONException("Unable to write JSONArray value at index: " + i, e);
                    }
                    needsComma = true;
                }
                if (indentFactor > 0) {
                    writer.write('\n');
                }
                JSONObject.indent(writer, indent);
            }
            writer.write(']');
            return writer;
        } catch (IOException e) {
            throw new JSONException(e);
        }
    }

    /**
     * Returns a java.util.List containing all of the elements in this array.
     * If an element in the array is a JSONArray or JSONObject it will also
     * be converted to a List and a Map respectively.
     * <p>
     * Warning: This method assumes that the data structure is acyclical.
     *
     * @return a java.util.List containing the elements of this array
     */
    public List<Object> toList() {
        List<Object> results = new ArrayList<Object>(this.myArrayList.size());
        for (Object element : this.myArrayList) {
            if (element == null || JSONObject.NULL.equals(element)) {
                results.add(null);
            } else if (element instanceof JSONArray) {
                results.add(((JSONArray) element).toList());
            } else if (element instanceof JSONObject) {
                results.add(((JSONObject) element).toMap());
            } else {
                results.add(element);
            }
        }
        return results;
    }

    /**
     * Check if JSONArray is empty.
     *
     * @return true if JSONArray is empty, otherwise false.
     */
    public boolean isEmpty() {
        return this.myArrayList.isEmpty();
    }
    
    /**
     * Create a new JSONException in a common format for incorrect conversions.
     * @param idx index of the item
     * @param valueType the type of value being coerced to
     * @param cause optional cause of the coercion failure
     * @return JSONException that can be thrown.
     */
    private static JSONException wrongValueFormatException(
            int idx,
            String valueType,
            Throwable cause) {
        return new JSONException(
                "JSONArray[" + idx + "] is not a " + valueType + "."
                , cause);
    }
    
    /**
     * Create a new JSONException in a common format for incorrect conversions.
     * @param idx index of the item
     * @param valueType the type of value being coerced to
     * @param cause optional cause of the coercion failure
     * @return JSONException that can be thrown.
     */
    private static JSONException wrongValueFormatException(
            int idx,
            String valueType,
            Object value,
            Throwable cause) {
        return new JSONException(
                "JSONArray[" + idx + "] is not a " + valueType + " (" + value + ")."
                , cause);
    }

}