@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

      builder.append(buf, 0, read);
    }
    assertEquals(expected, builder.toString());
    assertFullyRead(reader);

    // read all to one CharBuffer
    reader = new CharSequenceReader(charSequence);
    CharBuffer buf2 = CharBuffer.allocate(expected.length());
    assertEquals(expected.length() == 0 ? -1 : expected.length(), reader.read(buf2));
    Java8Compatibility.flip(buf2);

          return 0; // Not called.
        }
      }
    }
  }

  /** Returns a new CharBuffer identical to buf, except twice the capacity. */
  private static CharBuffer grow(CharBuffer buf) {
    char[] copy = Arrays.copyOf(buf.array(), buf.capacity() * 2);
    CharBuffer bigger = CharBuffer.wrap(copy);
    Java8Compatibility.position(bigger, buf.position());
    Java8Compatibility.limit(bigger, buf.limit());

          return 0; // Not called.
        }
      }
    }
  }

  /** Returns a new CharBuffer identical to buf, except twice the capacity. */
  private static CharBuffer grow(CharBuffer buf) {
    char[] copy = Arrays.copyOf(buf.array(), buf.capacity() * 2);
    CharBuffer bigger = CharBuffer.wrap(copy);
    Java8Compatibility.position(bigger, buf.position());
    Java8Compatibility.limit(bigger, buf.limit());

import com.google.common.annotations.J2ktIncompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.IOException;
import java.io.Reader;
import java.nio.CharBuffer;
import java.util.ArrayDeque;
import java.util.Queue;
import javax.annotation.CheckForNull;

/**
 * A class for reading lines of text. Provides the same functionality as {@link

import com.google.caliper.Param;
import com.google.caliper.api.VmOptions;
import java.io.IOException;
import java.io.StringReader;
import java.io.StringWriter;
import java.nio.Buffer;
import java.nio.CharBuffer;
import java.util.Random;

/**
 * Benchmarks for {@link CharStreams#copy}.
 *
 * <p>{@link CharStreams#copy} has type specific optimizations for various common Appendable and

import com.google.caliper.Param;
import com.google.caliper.api.VmOptions;
import java.io.IOException;
import java.io.StringReader;
import java.io.StringWriter;
import java.nio.Buffer;
import java.nio.CharBuffer;
import java.util.Random;

/**
 * Benchmarks for {@link CharStreams#copy}.
 *
 * <p>{@link CharStreams#copy} has type specific optimizations for various common Appendable and

    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();