Retry DateTimeTextProvider change

Redesign and make public
Single threading tests
Update TestNG version

pom.xml

@@ -117,7 +117,7 @@
           </includes>
           <argLine>-Xmx2G</argLine>
           <parallel>classes</parallel>
-          <threadCount>4</threadCount>
+          <threadCount>1</threadCount>
           <!-- remove slow SuiteHTMLReporter -->
           <properties>
             <property>
@@ -441,7 +441,7 @@
     <dependency>
       <groupId>org.testng</groupId>
       <artifactId>testng</artifactId>
-      <version>6.8</version><!-- Later versions need JDK 7 -->
+      <version>6.8.21</version><!-- Later versions need JDK 7 -->
       <scope>test</scope>
       <exclusions>
         <exclusion>

src/changes/changes.xml

@@ -9,6 +9,10 @@
 
     <!-- types are add, fix, remove, update -->
     <release version="1.3.5" date="SNAPSHOT" description="v1.3.5">
+      <action dev="pamalyshev" type="add" >
+        Add DateTimeTextProvider.setInstance() to allow the provider to be replaced.
+        See #69 and #70.
+      </action>
       <action dev="jodastephen" type="update" >
         Update to time-zone data 2017b.
       </action>

src/main/java/org/threeten/bp/format/DateTimeTextProvider.java

@@ -36,7 +36,6 @@
 import java.util.Map.Entry;
 import java.util.concurrent.atomic.AtomicReference;
 
-import org.threeten.bp.jdk8.Jdk8Methods;
 import org.threeten.bp.temporal.TemporalField;
 
 /**
@@ -47,27 +46,38 @@
  * This interface is a service provider that can be called by multiple threads.
  * Implementations must be thread-safe.
  * Implementations should cache the textual information.
+ * <p>
+ * This class has been made pubilc primarily for the benefit of Android.
  */
-abstract class DateTimeTextProvider {
+public abstract class DateTimeTextProvider {
+
+    private static final AtomicReference<DateTimeTextProvider> MUTABLE_PROVIDER = new AtomicReference<DateTimeTextProvider>();
 
     /**
      * Gets the provider.
      *
      * @return the provider, not null
      */
     static DateTimeTextProvider getInstance() {
-        return new SimpleDateTimeTextProvider();
+        return ProviderSingleton.PROVIDER;
     }
 
     /**
-     * Gets the available locales.
+     * Sets the provider to use.
+     * <p>
+     * This can only be invoked before {@link DateTimeTextProvider} class is used for formatting/parsing.
+     * Invoking this method at a later point will throw an exception.
      * 
-     * @return the locales
+     * @param provider  the provider to use
+     * @throws IllegalStateException if initialization has already occurred or another provider has been set
      */
-    public Locale[] getAvailableLocales() {
-        throw new UnsupportedOperationException();
+    public static void setInitializer(DateTimeTextProvider provider) {
+        if (!MUTABLE_PROVIDER.compareAndSet(null, provider)) {
+            throw new IllegalStateException("Provider was already set, possibly with a default during initialization");
+        }
     }
 
+    //-----------------------------------------------------------------------
     /**
      * Gets the text for the specified field, locale and style
      * for the purpose of printing.
@@ -102,4 +112,17 @@ public Locale[] getAvailableLocales() {
      */
     public abstract Iterator<Entry<String, Long>> getTextIterator(TemporalField field, TextStyle style, Locale locale);
 
+    //-----------------------------------------------------------------------
+    // use JVM class initializtion to lock the singleton without additional synchronization
+    static class ProviderSingleton {
+        static final DateTimeTextProvider PROVIDER = initialize();
+
+        // initialize the provider
+        static DateTimeTextProvider initialize() {
+            // Set the default initializer if none has been provided yet
+            MUTABLE_PROVIDER.compareAndSet(null, new SimpleDateTimeTextProvider());
+            return MUTABLE_PROVIDER.get();
+        }
+    }
+
 }

src/main/java/org/threeten/bp/format/SimpleDateTimeTextProvider.java

@@ -78,13 +78,6 @@ public int compare(Entry<String, Long> obj1, Entry<String, Long> obj2) {
     private final ConcurrentMap<Entry<TemporalField, Locale>, Object> cache =
             new ConcurrentHashMap<Entry<TemporalField, Locale>, Object>(16, 0.75f, 2);
 
-    //-----------------------------------------------------------------------
-    /** {@inheritDoc} */
-    @Override
-    public Locale[] getAvailableLocales() {
-        return DateFormatSymbols.getAvailableLocales();
-    }
-
     //-----------------------------------------------------------------------
     @Override
     public String getText(TemporalField field, long value, TextStyle style, Locale locale) {