cronet: Update to StandardCharsets and assertNotNull API's

cronet/src/main/java/io/grpc/cronet/CronetClientStream.java

@@ -42,7 +42,7 @@
 import io.grpc.internal.WritableBuffer;
 import java.nio.Buffer;
 import java.nio.ByteBuffer;
-import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
@@ -372,10 +372,10 @@ private void setGrpcHeaders(BidirectionalStream.Builder builder) {
     // String and byte array.
     byte[][] serializedHeaders = TransportFrameUtil.toHttp2Headers(headers);
     for (int i = 0; i < serializedHeaders.length; i += 2) {
-      String key = new String(serializedHeaders[i], Charset.forName("UTF-8"));
+      String key = new String(serializedHeaders[i], StandardCharsets.UTF_8);
       // TODO(ericgribkoff): log an error or throw an exception
       if (isApplicationHeader(key)) {
-        String value = new String(serializedHeaders[i + 1], Charset.forName("UTF-8"));
+        String value = new String(serializedHeaders[i + 1], StandardCharsets.UTF_8);
         builder.addHeader(key, value);
       }
     }
@@ -552,8 +552,8 @@ private void reportHeaders(List<Map.Entry<String, String>> headers, boolean endO
 
       byte[][] headerValues = new byte[headerList.size()][];
       for (int i = 0; i < headerList.size(); i += 2) {
-        headerValues[i] = headerList.get(i).getBytes(Charset.forName("UTF-8"));
-        headerValues[i + 1] = headerList.get(i + 1).getBytes(Charset.forName("UTF-8"));
+        headerValues[i] = headerList.get(i).getBytes(StandardCharsets.UTF_8);
+        headerValues[i + 1] = headerList.get(i + 1).getBytes(StandardCharsets.UTF_8);
       }
       Metadata metadata =
           InternalMetadata.newMetadata(TransportFrameUtil.toRawSerializedHeaders(headerValues));

cronet/src/test/java/io/grpc/cronet/CronetClientStreamTest.java

@@ -18,6 +18,7 @@
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.eq;
@@ -46,7 +47,7 @@
 import java.io.ByteArrayInputStream;
 import java.nio.Buffer;
 import java.nio.ByteBuffer;
-import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
@@ -102,7 +103,7 @@ void setStream(CronetClientStream stream) {
     @Override
     @SuppressWarnings("GuardedBy")
     public void run() {
-      assertTrue(stream != null);
+      assertNotNull(stream);
       stream.transportState().start(factory);
     }
   }
@@ -168,7 +169,7 @@ public void write() {
     for (int i = 0; i < 5; ++i) {
       requests[i] = "request" + i;
       buffers[i] = allocator.allocate(requests[i].length());
-      buffers[i].write(requests[i].getBytes(Charset.forName("UTF-8")), 0, requests[i].length());
+      buffers[i].write(requests[i].getBytes(StandardCharsets.UTF_8), 0, requests[i].length());
       // The 3rd and 5th writeFrame calls have flush=true.
       clientStream.abstractClientStreamSink().writeFrame(buffers[i], false, i == 2 || i == 4, 1);
     }
@@ -253,7 +254,7 @@ public void read() {
     callback.onReadCompleted(
         cronetStream,
         info,
-        createMessageFrame(new String("response1").getBytes(Charset.forName("UTF-8"))),
+        createMessageFrame("response1".getBytes(StandardCharsets.UTF_8)),
         false);
     // Haven't request any message, so no callback is called here.
     verify(clientListener, times(0)).messagesAvailable(isA(MessageProducer.class));
@@ -283,9 +284,9 @@ public void streamSucceeded() {
     verify(cronetStream, times(0)).write(isA(ByteBuffer.class), isA(Boolean.class));
     // Send the first data frame.
     CronetWritableBufferAllocator allocator = new CronetWritableBufferAllocator();
-    String request = new String("request");
+    String request = "request";
     WritableBuffer writableBuffer = allocator.allocate(request.length());
-    writableBuffer.write(request.getBytes(Charset.forName("UTF-8")), 0, request.length());
+    writableBuffer.write(request.getBytes(StandardCharsets.UTF_8), 0, request.length());
     clientStream.abstractClientStreamSink().writeFrame(writableBuffer, false, true, 1);
     ArgumentCaptor<ByteBuffer> bufferCaptor = ArgumentCaptor.forClass(ByteBuffer.class);
     verify(cronetStream, times(1)).write(bufferCaptor.capture(), isA(Boolean.class));
@@ -304,7 +305,7 @@ public void streamSucceeded() {
     callback.onReadCompleted(
         cronetStream,
         info,
-        createMessageFrame(new String("response").getBytes(Charset.forName("UTF-8"))),
+        createMessageFrame("response".getBytes(StandardCharsets.UTF_8)),
         false);
     verify(clientListener, times(1)).messagesAvailable(isA(MessageProducer.class));
     verify(cronetStream, times(2)).read(isA(ByteBuffer.class));
@@ -680,7 +681,7 @@ public void getUnaryRequest() {
         .newBidirectionalStreamBuilder(
             isA(String.class), isA(BidirectionalStream.Callback.class), isA(Executor.class));
 
-    byte[] msg = "request".getBytes(Charset.forName("UTF-8"));
+    byte[] msg = "request".getBytes(StandardCharsets.UTF_8);
     stream.writeMessage(new ByteArrayInputStream(msg));
     // We still haven't built the stream or sent anything.
     verify(cronetStream, times(0)).write(isA(ByteBuffer.class), isA(Boolean.class));

cronet/src/test/java/io/grpc/cronet/CronetClientTransportTest.java

@@ -17,7 +17,7 @@
 package io.grpc.cronet;
 
 import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertNotNull;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.times;
@@ -91,7 +91,7 @@ public void setUp() {
             false,
             false);
     Runnable callback = transport.start(clientTransportListener);
-    assertTrue(callback != null);
+    assertNotNull(callback);
     callback.run();
     verify(clientTransportListener).transportReady();
   }