@ElementTypesAreNonnullByDefault
public final class CharStreams {

  // 2K chars (4K bytes)
  private static final int DEFAULT_BUF_SIZE = 0x800;

  /** Creates a new {@code CharBuffer} for buffering reads or writes. */
  static CharBuffer createBuffer() {
    return CharBuffer.allocate(DEFAULT_BUF_SIZE);
  }

  private CharStreams() {}

  /**
   * Copies all characters between the {@link Readable} and {@link Appendable} objects. Does not

    assertEquals(-1, empty.read());
  }

  public void testExhaust_readable() throws IOException {
    CharBuffer buf = CharBuffer.wrap(ASCII);
    assertEquals(ASCII.length(), CharStreams.exhaust(buf));
    assertEquals(0, buf.remaining());
    assertEquals(0, CharStreams.exhaust(buf));

    CharBuffer empty = CharBuffer.wrap("");
    assertEquals(0, CharStreams.exhaust(empty));
    assertEquals(0, empty.remaining());
  }

    assertEquals(-1, empty.read());
  }

  public void testExhaust_readable() throws IOException {
    CharBuffer buf = CharBuffer.wrap(ASCII);
    assertEquals(ASCII.length(), CharStreams.exhaust(buf));
    assertEquals(0, buf.remaining());
    assertEquals(0, CharStreams.exhaust(buf));

    CharBuffer empty = CharBuffer.wrap("");
    assertEquals(0, CharStreams.exhaust(empty));
    assertEquals(0, empty.remaining());
  }

  }

  @J2ktIncompatible // J2kt CharBuffer does not implement CharSequence so not recognized as empty
  @GwtIncompatible // CharBuffer not available
  public void testToStringOmitEmptyValues_charBuffer() {
    String toTest =
        MoreObjects.toStringHelper(new TestClass())
            .omitEmptyValues()
            .add("field1", "Hello")
            .add("field2", CharBuffer.allocate(0))
            .toString();

      File file = getFile();
      Reader reader = new InputStreamReader(new FileInputStream(file), UTF_8);
      StringBuilder builder = new StringBuilder();
      CharBuffer buffer = CharBuffer.allocate(100);
      while (reader.read(buffer) != -1) {
        Java8Compatibility.flip(buffer);
        builder.append(buffer);
        Java8Compatibility.clear(buffer);
      }

          .put(Reader.class, new StringReader(""))
          .put(StringReader.class, new StringReader(""))
          .put(Buffer.class, ByteBuffer.allocate(0))
          .put(CharBuffer.class, CharBuffer.allocate(0))
          .put(ByteBuffer.class, ByteBuffer.allocate(0))
          .put(ShortBuffer.class, ShortBuffer.allocate(0))
          .put(IntBuffer.class, IntBuffer.allocate(0))

      File file = getFile();
      Reader reader = new InputStreamReader(new FileInputStream(file), UTF_8);
      StringBuilder builder = new StringBuilder();
      CharBuffer buffer = CharBuffer.allocate(100);
      while (reader.read(buffer) != -1) {
        Java8Compatibility.flip(buffer);
        builder.append(buffer);
        Java8Compatibility.clear(buffer);
      }

import java.io.Writer;
import java.lang.reflect.Method;
import java.lang.reflect.Type;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.nio.Buffer;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.DoubleBuffer;
import java.nio.FloatBuffer;
import java.nio.IntBuffer;
import java.nio.LongBuffer;
import java.nio.ShortBuffer;
import java.nio.charset.Charset;
import java.util.ArrayList;

          .put(Reader.class, new StringReader(""))
          .put(StringReader.class, new StringReader(""))
          .put(Buffer.class, ByteBuffer.allocate(0))
          .put(CharBuffer.class, CharBuffer.allocate(0))
          .put(ByteBuffer.class, ByteBuffer.allocate(0))
          .put(ShortBuffer.class, ShortBuffer.allocate(0))
          .put(IntBuffer.class, IntBuffer.allocate(0))

import java.io.Writer;
import java.lang.reflect.Method;
import java.lang.reflect.Type;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.nio.Buffer;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.DoubleBuffer;
import java.nio.FloatBuffer;
import java.nio.IntBuffer;
import java.nio.LongBuffer;
import java.nio.ShortBuffer;
import java.nio.charset.Charset;
import java.util.ArrayList;