hadoop示例代码

• 序列化和反序列化

        IntWritable writable = new IntWritable(10);        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();        DataOutputStream dataOutputStream = new DataOutputStream(byteArrayOutputStream);        writable.write(dataOutputStream);        dataOutputStream.close();        byte[] bytes = byteArrayOutputStream.toByteArray();        System.out.println(StringUtils.byteToHexString(bytes));        //解序列化        ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(bytes);        DataInputStream input = new DataInputStream(byteArrayInputStream);        IntWritable intWritable = new IntWritable();        intWritable.readFields(input);        input.close();        System.out.println(intWritable);

• writable对象的比较

        IntWritable int1 = new IntWritable(1);        IntWritable int2 = new IntWritable(3);        RawComparator<IntWritable> comparator = WritableComparator.get(IntWritable.class);        System.out.println(comparator.compare(int1,int2));        //也可以直接比较字节流，不需要反序列化，问题是怎么定位这个字节流呢        System.out.println(comparator.compare(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2));