java中int与byte，以及long与byte之间的转换

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原文链接：http://blog.csdn.net/zgyulongfei/article/details/7738970

做项目时候根据协议在发送网络流的时候需要将所有int及long转换成byte，因此写了以下的转换方法，希望能帮助到需要的朋友 ^_^

闲话少说，直接上码。

public class Utilities {public static byte[] int2Bytes(int num) {byte[] byteNum = new byte[4];for (int ix = 0; ix < 4; ++ix) {int offset = 32 - (ix + 1) * 8;byteNum[ix] = (byte) ((num >> offset) & 0xff);}return byteNum;}public static int bytes2Int(byte[] byteNum) {int num = 0;for (int ix = 0; ix < 4; ++ix) {num <<= 8;num |= (byteNum[ix] & 0xff);}return num;}public static byte int2OneByte(int num) {return (byte) (num & 0x000000ff);}public static int oneByte2Int(byte byteNum) {

                //针对正数的intreturn byteNum > 0 ? byteNum : (128 + (128 + byteNum));}public static byte[] long2Bytes(long num) {byte[] byteNum = new byte[8];for (int ix = 0; ix < 8; ++ix) {int offset = 64 - (ix + 1) * 8;byteNum[ix] = (byte) ((num >> offset) & 0xff);}return byteNum;}public static long bytes2Long(byte[] byteNum) {long num = 0;for (int ix = 0; ix < 8; ++ix) {num <<= 8;num |= (byteNum[ix] & 0xff);}return num;}}

public class TestMain {public static void main(String[] args) {int num = 129;System.out.println("测试的int值为:" + num);byte[] int2bytes = Utilities.int2Bytes(num);System.out.printf("int转成bytes: ");for (int i = 0; i < 4; ++i) {System.out.print(int2bytes[i] + " ");}System.out.println();int bytes2int = Utilities.bytes2Int(int2bytes);System.out.println("bytes转行成int: " + bytes2int);byte int2OneByte = Utilities.int2OneByte(num);System.out.println("int转行成one byte: " + int2OneByte);int oneByte2Int = Utilities.oneByte2Int(int2OneByte);System.out.println("one byte转行成int: " + oneByte2Int);System.out.println();long longNum = 100000;System.out.println("测试的long值为：" + longNum);byte[] long2Bytes = Utilities.long2Bytes(longNum);System.out.printf("long转行成bytes: ");for (int ix = 0; ix < long2Bytes.length; ++ix) {System.out.print(long2Bytes[ix] + " ");}System.out.println();long bytes2Long = Utilities.bytes2Long(long2Bytes);System.out.println("bytes转行成long: " + bytes2Long);}}

测试结果如下：

测试的int值为:156int转成bytes: 0 0 0 -100 bytes转行成int: 156int转行成one byte: -100one byte转行成int: 156测试的long值为：100000long转行成bytes: 0 0 0 0 0 1 -122 -96 bytes转行成long: 100000