java中float与byte[]的互转

FROM:http://tjmljw.iteye.com/blog/1767716

起因：想把一个float[]转换成内存数据，查了一下，下面两个方法可以将float转成byte[]。

方法一

Java代码


import java.nio.ByteBuffer;

import java.util.ArrayList;

float buffer = 0f;

ByteBuffer bbuf = ByteBuffer.allocate(4);

bbuf.putFloat(buffer);

byte[] bBuffer = bbuf.array();

bBuffer=this.dataValueRollback(bBuffer);

//数值反传

private byte[] dataValueRollback(byte[] data) {

ArrayList<Byte> al = new ArrayList<Byte>();

for (int i = data.length - 1; i >= 0; i--) {

al.add(data[i]);

}

byte[] buffer = new byte[al.size()];

for (int i = 0; i <= buffer.length - 1; i++) {

buffer[i] = al.get(i);

}

return buffer;

}

方法二

先用 Float.floatToIntBits(f)转换成int

再通过如下方法转成byte []

Java代码


/**

* 将int类型的数据转换为byte数组 原理：将int数据中的四个byte取出，分别存储

*

* @param n int数据

* @return 生成的byte数组

*/

public static byte[] intToBytes2(int n) {

byte[] b = new byte[4];

for (int i = 0; i < 4; i++) {

b[i] = (byte) (n >> (24 - i * 8));

}

return b;

}

/**

* 将byte数组转换为int数据

*

* @param b 字节数组

* @return 生成的int数据

*/

public static int byteToInt2(byte[] b) {

return (((int) b[0]) << 24) + (((int) b[1]) << 16)

+ (((int) b[2]) << 8) + b[3];

}

方法三（这个是我在用的）：

Java代码


/**

* 浮点转换为字节

*

* @param f

* @return

*/

public static byte[] float2byte(float f) {

// 把float转换为byte[]

int fbit = Float.floatToIntBits(f);

byte[] b = new byte[4];

for (int i = 0; i < 4; i++) {

b[i] = (byte) (fbit >> (24 - i * 8));

}

// 翻转数组

int len = b.length;

// 建立一个与源数组元素类型相同的数组

byte[] dest = new byte[len];

// 为了防止修改源数组，将源数组拷贝一份副本

System.arraycopy(b, 0, dest, 0, len);

byte temp;

// 将顺位第i个与倒数第i个交换

for (int i = 0; i < len / 2; ++i) {

temp = dest[i];

dest[i] = dest[len - i - 1];

dest[len - i - 1] = temp;

}

return dest;

}

/**

* 字节转换为浮点

*

* @param b 字节（至少4个字节）

* @param index 开始位置

* @return

*/

public static float byte2float(byte[] b, int index) {

int l;

l = b[index + 0];

l &= 0xff;

l |= ((long) b[index + 1] << 8);

l &= 0xffff;

l |= ((long) b[index + 2] << 16);

l &= 0xffffff;

l |= ((long) b[index + 3] << 24);

return Float.intBitsToFloat(l);

}

2013-05-06 add

title Java基本类型与byte数组之间相互转换

from http://blog.sina.com.cn/s/blog_7a35101201012n0b.html

Java代码


package com.my.wxf4j.utils;

import java.nio.charset.Charset;

public class ByteUtil

{

public static byte[] getBytes(short data)

{

byte[] bytes = new byte[2];

bytes[0] = (byte) (data & 0xff);

bytes[1] = (byte) ((data & 0xff00) >> 8);

return bytes;

}

public static byte[] getBytes(char data)

{

byte[] bytes = new byte[2];

bytes[0] = (byte) (data);

bytes[1] = (byte) (data >> 8);

return bytes;

}

public static byte[] getBytes(int data)

{

byte[] bytes = new byte[4];

bytes[0] = (byte) (data & 0xff);

bytes[1] = (byte) ((data & 0xff00) >> 8);

bytes[2] = (byte) ((data & 0xff0000) >> 16);

bytes[3] = (byte) ((data & 0xff000000) >> 24);

return bytes;

}

public static byte[] getBytes(long data)

{

byte[] bytes = new byte[8];

bytes[0] = (byte) (data & 0xff);

bytes[1] = (byte) ((data >> 8) & 0xff);

bytes[2] = (byte) ((data >> 16) & 0xff);

bytes[3] = (byte) ((data >> 24) & 0xff);

bytes[4] = (byte) ((data >> 32) & 0xff);

bytes[5] = (byte) ((data >> 40) & 0xff);

bytes[6] = (byte) ((data >> 48) & 0xff);

bytes[7] = (byte) ((data >> 56) & 0xff);

return bytes;

}

public static byte[] getBytes(float data)

{

int intBits = Float.floatToIntBits(data);

return getBytes(intBits);

}

public static byte[] getBytes(double data)

{

long intBits = Double.doubleToLongBits(data);

return getBytes(intBits);

}

public static byte[] getBytes(String data, String charsetName)

{

Charset charset = Charset.forName(charsetName);

return data.getBytes(charset);

}

public static byte[] getBytes(String data)

{

return getBytes(data, "GBK");

}

public static short getShort(byte[] bytes)

{

return (short) ((0xff & bytes[0]) | (0xff00 & (bytes[1] << 8)));

}

public static char getChar(byte[] bytes)

{

return (char) ((0xff & bytes[0]) | (0xff00 & (bytes[1] << 8)));

}

public static int getInt(byte[] bytes)

{

return (0xff & bytes[0]) | (0xff00 & (bytes[1] << 8)) | (0xff0000 & (bytes[2] << 16)) | (0xff000000 & (bytes[3] << 24));

}

public static long getLong(byte[] bytes)

{

return(0xffL & (long)bytes[0]) | (0xff00L & ((long)bytes[1] << 8)) | (0xff0000L & ((long)bytes[2] << 16)) | (0xff000000L & ((long)bytes[3] << 24))

| (0xff00000000L & ((long)bytes[4] << 32)) | (0xff0000000000L & ((long)bytes[5] << 40)) | (0xff000000000000L & ((long)bytes[6] << 48)) | (0xff00000000000000L & ((long)bytes[7] << 56));

}

public static float getFloat(byte[] bytes)

{

return Float.intBitsToFloat(getInt(bytes));

}

public static double getDouble(byte[] bytes)

{

long l = getLong(bytes);

System.out.println(l);

return Double.longBitsToDouble(l);

}

public static String getString(byte[] bytes, String charsetName)

{

return new String(bytes, Charset.forName(charsetName));

}

public static String getString(byte[] bytes)

{

return getString(bytes, "GBK");

}

public static void main(String[] args)

{

short s = 122;

int i = 122;

long l = 1222222;

char c = 'a';

float f = 122.22f;

double d = 122.22;

String string = "我是好孩子";

System.out.println(s);

System.out.println(i);

System.out.println(l);

System.out.println(c);

System.out.println(f);

System.out.println(d);

System.out.println(string);

System.out.println("**************");

System.out.println(getShort(getBytes(s)));

System.out.println(getInt(getBytes(i)));

System.out.println(getLong(getBytes(l)));

System.out.println(getChar(getBytes(c)));

System.out.println(getFloat(getBytes(f)));

System.out.println(getDouble(getBytes(d)));

System.out.println(getString(getBytes(string)));

}

}