byte 和boolean，int，String，char,short,long之间的转换

今日偶来无事，随手翻阅jdk的源码，发现java.io包下有一个bytes类，但是在api中有没有找到相关的说明，于是出于好奇心就将其打开了，才知道原来里面都是好东西，可能是他自己用的，并没有提供给外部来使用，前段时间简析二进制文件就用到这些知识当时在网上找了很久也是大费苦心，呵呵，，现在可好了，原来源码中就有，而且稳定性比自己写的要高很多，现在我就将其贴出来给大家，让使用的人少走弯路，

/*

* @(#)Bits.java 1.7 05/11/17

*

* Copyright 2006 Sun Microsystems, Inc. All rights reserved.

* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.

*/

package java.io;

/**

* Utility methods for packing/unpacking primitive values in/out of byte arrays

* using big-endian byte ordering.

*/

class Bits {

/*

* Methods for unpacking primitive values from byte arrays starting at

* given offsets.

*/

static boolean getBoolean(byte[] b, int off) {

return b[off] != 0;

}

static char getChar(byte[] b, int off) {

return (char) (((b[off + 1] & 0xFF) << 0) +

((b[off + 0]) << 8));

}

static short getShort(byte[] b, int off) {

return (short) (((b[off + 1] & 0xFF) << 0) +

((b[off + 0]) << 8));

}

static int getInt(byte[] b, int off) {

return ((b[off + 3] & 0xFF) << 0) +

((b[off + 2] & 0xFF) << 8) +

((b[off + 1] & 0xFF) << 16) +

((b[off + 0]) << 24);

}

static float getFloat(byte[] b, int off) {

int i = ((b[off + 3] & 0xFF) << 0) +

((b[off + 2] & 0xFF) << 8) +

((b[off + 1] & 0xFF) << 16) +

((b[off + 0]) << 24);

return Float.intBitsToFloat(i);

}

static long getLong(byte[] b, int off) {

return ((b[off + 7] & 0xFFL) << 0) +

((b[off + 6] & 0xFFL) << 8) +

((b[off + 5] & 0xFFL) << 16) +

((b[off + 4] & 0xFFL) << 24) +

((b[off + 3] & 0xFFL) << 32) +

((b[off + 2] & 0xFFL) << 40) +

((b[off + 1] & 0xFFL) << 48) +

(((long) b[off + 0]) << 56);

}

static double getDouble(byte[] b, int off) {

long j = ((b[off + 7] & 0xFFL) << 0) +

((b[off + 6] & 0xFFL) << 8) +

((b[off + 5] & 0xFFL) << 16) +

((b[off + 4] & 0xFFL) << 24) +

((b[off + 3] & 0xFFL) << 32) +

((b[off + 2] & 0xFFL) << 40) +

((b[off + 1] & 0xFFL) << 48) +

(((long) b[off + 0]) << 56);

return Double.longBitsToDouble(j);

}

/*

* Methods for packing primitive values into byte arrays starting at given

* offsets.

*/

static void putBoolean(byte[] b, int off, boolean val) {

b[off] = (byte) (val ? 1 : 0);

}

static void putChar(byte[] b, int off, char val) {

b[off + 1] = (byte) (val >>> 0);

b[off + 0] = (byte) (val >>> 8);

}

static void putShort(byte[] b, int off, short val) {

b[off + 1] = (byte) (val >>> 0);

b[off + 0] = (byte) (val >>> 8);

}

static void putInt(byte[] b, int off, int val) {

b[off + 3] = (byte) (val >>> 0);

b[off + 2] = (byte) (val >>> 8);

b[off + 1] = (byte) (val >>> 16);

b[off + 0] = (byte) (val >>> 24);

}

static void putFloat(byte[] b, int off, float val) {

int i = Float.floatToIntBits(val);

b[off + 3] = (byte) (i >>> 0);

b[off + 2] = (byte) (i >>> 8);

b[off + 1] = (byte) (i >>> 16);

b[off + 0] = (byte) (i >>> 24);

}

static void putLong(byte[] b, int off, long val) {

b[off + 7] = (byte) (val >>> 0);

b[off + 6] = (byte) (val >>> 8);

b[off + 5] = (byte) (val >>> 16);

b[off + 4] = (byte) (val >>> 24);

b[off + 3] = (byte) (val >>> 32);

b[off + 2] = (byte) (val >>> 40);

b[off + 1] = (byte) (val >>> 48);

b[off + 0] = (byte) (val >>> 56);

}

static void putDouble(byte[] b, int off, double val) {

long j = Double.doubleToLongBits(val);

b[off + 7] = (byte) (j >>> 0);

b[off + 6] = (byte) (j >>> 8);

b[off + 5] = (byte) (j >>> 16);

b[off + 4] = (byte) (j >>> 24);

b[off + 3] = (byte) (j >>> 32);

b[off + 2] = (byte) (j >>> 40);

b[off + 1] = (byte) (j >>> 48);

b[off + 0] = (byte) (j >>> 56);

}

}