core, alts, cronet: fix ByteBuffer covariant method usages

core/src/main/java/io/grpc/internal/CompositeReadableBuffer.java

@@ -102,18 +102,15 @@ public int readInternal(ReadableBuffer buffer, int length) {
 
   @Override
   public void readBytes(final ByteBuffer dest) {
-    // Use Buffer instead of ByteBuffer for JDK 9+ compatibility.
-    final Buffer destAsBuffer = dest;
     execute(new ReadOperation() {
       @Override
       public int readInternal(ReadableBuffer buffer, int length) {
-        // Change the limit so that only lengthToCopy bytes are available.
-        int prevLimit = destAsBuffer.limit();
-        destAsBuffer.limit(destAsBuffer.position() + length);
+        int prevLimit = dest.limit();
+        ((Buffer) dest).limit(dest.position() + length);
 
         // Write the bytes and restore the original limit.
         buffer.readBytes(dest);
-        destAsBuffer.limit(prevLimit);
+        ((Buffer) dest).limit(prevLimit);
         return 0;
       }
     }, dest.remaining());

core/src/main/java/io/grpc/internal/ReadableBuffers.java

@@ -210,8 +210,7 @@ public int arrayOffset() {
    * A {@link ReadableBuffer} that is backed by a {@link ByteBuffer}.
    */
   private static class ByteReadableBufferWrapper extends AbstractReadableBuffer {
-    // Use Buffer instead of ByteBuffer for JDK 9+ compatibility.
-    final Buffer bytes;
+    final ByteBuffer bytes;
 
     ByteReadableBufferWrapper(ByteBuffer bytes) {
       this.bytes = Preconditions.checkNotNull(bytes, "bytes");
@@ -225,19 +224,19 @@ public int readableBytes() {
     @Override
     public int readUnsignedByte() {
       checkReadable(1);
-      return ((ByteBuffer) bytes).get() & 0xFF;
+      return bytes.get() & 0xFF;
     }
 
     @Override
     public void skipBytes(int length) {
       checkReadable(length);
-      bytes.position(bytes.position() + length);
+      ((Buffer) bytes).position(bytes.position() + length);
     }
 
     @Override
     public void readBytes(byte[] dest, int destOffset, int length) {
       checkReadable(length);
-      ((ByteBuffer) bytes).get(dest, destOffset, length);
+      bytes.get(dest, destOffset, length);
     }
 
     @Override
@@ -248,10 +247,10 @@ public void readBytes(ByteBuffer dest) {
 
       // Change the limit so that only length bytes are available.
       int prevLimit = bytes.limit();
-      bytes.limit(bytes.position() + length);
+      ((Buffer) bytes).limit(bytes.position() + length);
 
       // Write the bytes and restore the original limit.
-      dest.put((ByteBuffer) bytes);
+      dest.put(bytes);
       bytes.limit(prevLimit);
     }
 
@@ -260,21 +259,21 @@ public void readBytes(OutputStream dest, int length) throws IOException {
       checkReadable(length);
       if (hasArray()) {
         dest.write(array(), arrayOffset(), length);
-        bytes.position(bytes.position() + length);
+        ((Buffer) bytes).position(bytes.position() + length);
       } else {
         // The buffer doesn't support array(). Copy the data to an intermediate buffer.
         byte[] array = new byte[length];
-        ((ByteBuffer) bytes).get(array);
+        bytes.get(array);
         dest.write(array);
       }
     }
 
     @Override
     public ByteReadableBufferWrapper readBytes(int length) {
       checkReadable(length);
-      ByteBuffer buffer = ((ByteBuffer) bytes).duplicate();
+      ByteBuffer buffer = bytes.duplicate();
       ((Buffer) buffer).limit(bytes.position() + length);
-      bytes.position(bytes.position() + length);
+      ((Buffer) bytes).position(bytes.position() + length);
       return new ByteReadableBufferWrapper(buffer);
     }
 
@@ -285,7 +284,7 @@ public boolean hasArray() {
 
     @Override
     public byte[] array() {
-      return ((ByteBuffer) bytes).array();
+      return bytes.array();
     }
 
     @Override

core/src/test/java/io/grpc/internal/CompositeReadableBufferTest.java

@@ -23,6 +23,7 @@
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
+import java.nio.Buffer;
 import java.nio.ByteBuffer;
 import org.junit.After;
 import org.junit.Before;
@@ -119,17 +120,17 @@ public void readByteBufferShouldSucceed() {
     ByteBuffer byteBuffer = ByteBuffer.allocate(EXPECTED_VALUE.length());
     int remaining = EXPECTED_VALUE.length();
 
-    byteBuffer.limit(1);
+    ((Buffer) byteBuffer).limit(1);
     composite.readBytes(byteBuffer);
     remaining--;
     assertEquals(remaining, composite.readableBytes());
 
-    byteBuffer.limit(byteBuffer.limit() + 5);
+    ((Buffer) byteBuffer).limit(byteBuffer.limit() + 5);
     composite.readBytes(byteBuffer);
     remaining -= 5;
     assertEquals(remaining, composite.readableBytes());
 
-    byteBuffer.limit(byteBuffer.limit() + remaining);
+    ((Buffer) byteBuffer).limit(byteBuffer.limit() + remaining);
     composite.readBytes(byteBuffer);
     assertEquals(0, composite.readableBytes());
     assertEquals(EXPECTED_VALUE, new String(byteBuffer.array(), UTF_8));

core/src/test/java/io/grpc/internal/ReadableBufferTestBase.java

@@ -21,6 +21,7 @@
 import static org.junit.Assert.assertEquals;
 
 import java.io.ByteArrayOutputStream;
+import java.nio.Buffer;
 import java.nio.ByteBuffer;
 import java.util.Arrays;
 import org.junit.Test;
@@ -86,7 +87,7 @@ public void readToByteBufferShouldSucceed() {
     ReadableBuffer buffer = buffer();
     ByteBuffer byteBuffer = ByteBuffer.allocate(msg.length());
     buffer.readBytes(byteBuffer);
-    byteBuffer.flip();
+    ((Buffer) byteBuffer).flip();
     byte[] array = new byte[msg.length()];
     byteBuffer.get(array);
     assertArrayEquals(msg.getBytes(UTF_8), array);
@@ -98,7 +99,7 @@ public void partialReadToByteBufferShouldSucceed() {
     ReadableBuffer buffer = buffer();
     ByteBuffer byteBuffer = ByteBuffer.allocate(2);
     buffer.readBytes(byteBuffer);
-    byteBuffer.flip();
+    ((Buffer) byteBuffer).flip();
     byte[] array = new byte[2];
     byteBuffer.get(array);
     assertArrayEquals(new byte[]{'h', 'e'}, array);