将整数转换为字节数组(Java)

问题描述

将 Integer 转换为 Byte Array 的快速方法是什么?

what's a fast way to convert an Integer into a Byte Array?

例如0xAABBCCDD =>{AA、BB、CC、DD}

推荐答案

查看ByteBuffer 类.

ByteBuffer b = ByteBuffer.allocate(4);
//b.order(ByteOrder.BIG_ENDIAN); // optional, the initial order of a byte buffer is always BIG_ENDIAN.
b.putInt(0xAABBCCDD);

byte[] result = b.array();

设置字节顺序确保result[0] == 0xAA, result[1] == 0xBB, result[2] == 0xCC 和 result[3] == 0xDD.

Setting the byte order ensures that result[0] == 0xAA, result[1] == 0xBB, result[2] == 0xCC and result[3] == 0xDD.

或者，您也可以手动完成:

Or alternatively, you could do it manually:

byte[] toBytes(int i)
{
  byte[] result = new byte[4];

  result[0] = (byte) (i >> 24);
  result[1] = (byte) (i >> 16);
  result[2] = (byte) (i >> 8);
  result[3] = (byte) (i /*>> 0*/);

  return result;
}

ByteBuffer 类是为这种脏手任务设计的.事实上，私有的 java.nio.Bits 定义了这些由 ByteBuffer.putInt() 使用的辅助方法:

The ByteBuffer class was designed for such dirty hands tasks though. In fact the private java.nio.Bits defines these helper methods that are used by ByteBuffer.putInt():

private static byte int3(int x) { return (byte)(x >> 24); }
private static byte int2(int x) { return (byte)(x >> 16); }
private static byte int1(int x) { return (byte)(x >>  8); }
private static byte int0(int x) { return (byte)(x >>  0); }

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