public interface Writable {void write(DataOutput out) throws IOException;void readFields(DataInput in) throws IOException;
}

  @Overridepublic void readFields(DataInput in) throws IOException {value = in.readBoolean();}@Overridepublic void write(DataOutput out) throws IOException {out.writeBoolean(value);}

public interface RawComparator<T> extends Comparator<T> {public int compare(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2);
}

  public int compare(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2) {try {buffer.reset(b1, s1, l1);                   // parse key1
      key1.readFields(buffer);buffer.reset(b2, s2, l2);                   // parse key2
      key2.readFields(buffer);buffer.reset(null, 0, 0);                   // clean up reference} catch (IOException e) {throw new RuntimeException(e);}return compare(key1, key2);                   // compare them}

  public static class Comparator extends WritableComparator {public Comparator() {super(BooleanWritable.class);}@Overridepublic int compare(byte[] b1, int s1, int l1,byte[] b2, int s2, int l2) {return compareBytes(b1, s1, l1, b2, s2, l2);}}// 注册static {WritableComparator.define(BooleanWritable.class, new Comparator());}

  public static WritableComparator get(Class<? extends WritableComparable> c, Configuration conf) {WritableComparator comparator = comparators.get(c);if (comparator == null) {      forceInit(c);comparator = comparators.get(c);if (comparator == null) {comparator = new WritableComparator(c, conf, true);}}
    ReflectionUtils.setConf(comparator, conf);return comparator;}

private Class declaredClass;
private Object instance;
private Configuration conf;