Java 数据类型转换（转换成字节型）

package com.mystudypro.byteutil;
import java.io.UnsupportedEncodingException;

public class ConToByte {
/**
* double转换byte
* @param  arr  byte[]
* @param  param    double   double类型的参数
* @param  index  int
*/

public static void putDouble(byte[] arr, double param, int index) {

int len = (index - 1) + 8;
int arrLen = arr.length;
boolean b = isOutOfArrLength(arrLen, len);   //判断当前数组长度是否大于转换的数组长度
Long l = Double.doubleToLongBits(param);
if (b) {
for (int i = 7; i >=0; i--) {
　　arr[index + i] = l.byteValue();
　　l = l >> 8;
}
} else {
            // 如果当前数组长度小于转换的数组长度，就根据index截取转换的数组元素
             l = l>>(8*index);
            for(int j= arrLen-index-1;j>=0;j--){
                arr[index+j] = l.byteValue();
                l = l>>8;
            }
        }
}

/**
* float转换byte
*
* @param  arr   byte[]
* @param  param    float  float类型的参数
* @param  index  int
*/

public static void putFloat(byte[] arr, float param, int index) {
int len = (index - 1) + 4;
int arrLen = arr.length;
boolean b = isOutOfArrLength(arrLen, len);    //判断当前数组长度是否大于转换的数组长度
int l = Float.floatToIntBits(param);
if (b) {
for (int i = 3; i >=0; i--) {
arr[index + i] = new Integer(l).byteValue();
l = l >> 8;
}
} else {
            // 如果当前数组长度小于转换的数组长度，就根据index截取转换的数组元素
            l = l>>(8*index);
            for(int j=arrLen-index-1;j>=0;j--){
                arr[index+j] =  new Integer(l).byteValue();
                 l =l>>8;
            }
        }
}

/**
* 字符到字节转换
*
* @param  arr   byte[]
* @param  ch     char   char类型的参数
* @param  index   int
* @return
*/

public static void putChar(byte[] arr, char ch, int index) {
int len = (index - 1) + 4;
boolean b = isOutOfArrLength(arr.length, len);      //判断当前数组长度是否大于转换的数组长度
if (b) {
int temp = (int) ch;
for (int i = 1; i >=0; i--) {
arr[index + i] = new Integer(temp & 0xff).byteValue();
temp = temp >> 8;
}
}
}

/**
* 转换long型为byte数组
*
* @param  arr  byte[]
* @param  param    long
* @param  index  int
*/

public static void putLong(byte[] arr, long param, int index) {
int len = (index - 1) + 8;
int arrLen = arr.length;
boolean b = isOutOfArrLength(arrLen, len);    //判断当前数组长度是否大于转换的数组长度
if (b) {
arr[index + 0] = (byte) ((param >> 56) & 0xff);
arr[index + 1] = (byte) ((param >> 48) & 0xff);
arr[index + 2] = (byte) ((param >> 40) & 0xff);
arr[index + 3] = (byte) ((param >> 32) & 0xff);
arr[index + 4] = (byte) ((param >> 24) & 0xff);
arr[index + 5] = (byte) ((param >> 16) & 0xff);
arr[index + 6] = (byte) ((param >> 8) & 0xff);
arr[index + 7] = (byte) (param & 0xff);
} else {
// 如果当前数组长度小于转换的数组长度，就根据index截取转换的数组元素
param = param >> (8*index);
for(int i=arrLen-index-1;i>=0;i--){
arr[index+i] =  (byte) (param & 0xff);
param = param >> 8;
              }
        }
}

/**
* int类型转换成byte数组
*
* @param arr byte[]
* @param param  int int类型的参数
* @param index  int
*/

public static void putInt(byte[] arr, int param, int index) {
int len = (index - 1) + 4;
boolean b = isOutOfArrLength(arr.length, len);     //判断当前数组长度是否大于转换的数组长度
if (b) {
arr[index + 0] = (byte) ((param >> 24) & 0xff);
arr[index + 1] = (byte) ((param >> 16) & 0xff);
arr[index + 2] = (byte) ((param >> 8) & 0xff);
arr[index + 3] = (byte) (param & 0xff);
}
}

/**
* short类型转换成byte数组
*
* @param arr   byte[]
* @param param  short
* @param index  int
*/

public static void putShort(byte[] arr, short param, int index) {
int len = (index - 1) + 2;
boolean b = isOutOfArrLength(arr.length, len);        //判断当前数组长度是否大于转换的数组长度
if (b) {
arr[index + 0] = (byte) ((param >> 8) & 0xff);
arr[index + 1] = (byte) (param & 0xff);
}
}

/**
* 字符串转换成byte数组
*
* @param arr  byte[]
* @param str  String
* @param index  int
* @throws java.io.UnsupportedEncodingException
*/

public static void putString(byte[] arr, String str, int index) {
try {
byte[] bb = str.getBytes("GBK");
int len = index + bb.length;
boolean b = isOutOfArrLength(arr.length, len);
if (b) {
for (int i = 0; i < bb.length; i++) {
arr[index + i] = bb[i];
}
} else {
        // 如果当前数组长度小于转换的数组长度，就根据index截取转换的数组元素
　　　　 for(int j=0;j<arr.length-index;j++){
                    arr[index+j] = bb[j];
                }
            }
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}

/**
* 判断数组下标是否越界
*
* @param arrLength
*            数组总长度
* @param index
*            数组偏移量
* @return
*/

public static boolean isOutOfArrLength(int arrLength, int index) {
boolean b;
if (arrLength > index) {
b = true;
} else {
b = false;
}
return b;
}
}