JavaDemo——byte[]与其他数据类型的大端小端转换工具类

大端：高位字节放在内存的低地址位置；

小端：低位字节放在内存的低地址位置；

东拼西凑的Demo：

/**
 * createtime:2018年6月4日下午6:24:01
 */
package cn.zectec.synchroserver.codec;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;

/**
 * @author XWF
 *
 */
public class CodecUtil {
	
	/**
	 * 向将bytes添加到另一个bytes结尾，并返回位置
	 * @param buff 目标数组
	 * @param pos 目标数组放置的起始位置
	 * @param lens 添加的长度
	 * @param dx 要添加的数组
	 * @return lens添加的长度
	 */
	public static int addToBuff(byte[] buff, int pos, int lens, byte[] dx) {
        System.arraycopy(dx, 0, buff, pos, lens);
        return lens;
    }
	
	/**
	 * 获得bytes的一段数据
	 * @param buff 原byte数组
	 * @param startPos 起始位置
	 * @param lenth 获取的长度
	 * @return 返回获得的byte数组
	 */
	public static byte[] getFromBuff(byte[] buff,int startPos,int lenth) {
		byte[] bytes = new byte[lenth];
		System.arraycopy(buff, startPos, bytes, 0, lenth);
		return bytes;
	}
	
	/**
	 * double转byte数组，小端模式
	 * @param d
	 * @return
	 */
	public static byte[] doubleToBytes_Little(double d){
        long l = Double.doubleToLongBits(d);
        byte b[] = new byte[8];
        b[7] = (byte)  (0xff & (l >> 56));
        b[6] = (byte)  (0xff & (l >> 48));
        b[5] = (byte)  (0xff & (l >> 40));
        b[4] = (byte)  (0xff & (l >> 32));
        b[3] = (byte)  (0xff & (l >> 24));
        b[2] = (byte)  (0xff & (l >> 16));
        b[1] = (byte)  (0xff & (l >> 8));
        b[0] = (byte)  (0xff & l);
        return b;
    }
	
	/**
	 * double转byte数组，大端模式
	 * @param d
	 * @return
	 */
	public static byte[] doubleToBytes_Big(double d){
        long l = Double.doubleToLongBits(d);
        byte b[] = new byte[8];
        b[0] = (byte)  (0xff & (l >> 56));
        b[1] = (byte)  (0xff & (l >> 48));
        b[2] = (byte)  (0xff & (l >> 40));
        b[3] = (byte)  (0xff & (l >> 32));
        b[4] = (byte)  (0xff & (l >> 24));
        b[5] = (byte)  (0xff & (l >> 16));
        b[6] = (byte)  (0xff & (l >> 8));
        b[7] = (byte)  (0xff & l);
        return b;
    }
	
	/**
	 * byte数组转double
	 * @param bytes 8位byte数组
	 * @param littleEndian 是否是小端模式
	 * @return
	 */
	public static double bytesToDouble(byte[] bytes, boolean littleEndian) {
        ByteBuffer buffer = ByteBuffer.wrap(bytes,0,8);
        if(littleEndian){
            // ByteBuffer.order(ByteOrder) 方法指定字节序,即大小端模式(BIG_ENDIAN/LITTLE_ENDIAN)
            // ByteBuffer 默认为大端(BIG_ENDIAN)模式 
            buffer.order(ByteOrder.LITTLE_ENDIAN);
        }
        long l = buffer.getLong();
        return Double.longBitsToDouble(l);
    }
	
	/**
	 * long转byte数组，小端模式
	 * @param l
	 * @return
	 */
	public static byte[] longToBytes_Little(long l) {
		byte b[] = new byte[8];
		b[7] = (byte)  (0xff & (l >> 56));
		b[6] = (byte)  (0xff & (l >> 48));
		b[5] = (byte)  (0xff & (l >> 40));
		b[4] = (byte)  (0xff & (l >> 32));
		b[3] = (byte)  (0xff & (l >> 24));
		b[2] = (byte)  (0xff & (l >> 16));
		b[1] = (byte)  (0xff & (l >> 8));
		b[0] = (byte)  (0xff & l);
		return b;
	}
	
	/**
	 * long转byte数组，大端模式
	 * @param l
	 * @return
	 */
	public static byte[] longToBytes_Big(long l) {
        byte b[] = new byte[8];
        b[0] = (byte)  (0xff & (l >> 56));
        b[1] = (byte)  (0xff & (l >> 48));
        b[2] = (byte)  (0xff & (l >> 40));
        b[3] = (byte)  (0xff & (l >> 32));
        b[4] = (byte)  (0xff & (l >> 24));
        b[5] = (byte)  (0xff & (l >> 16));
        b[6] = (byte)  (0xff & (l >> 8));
        b[7] = (byte)  (0xff & l);
        return b;
	}
	
	/**
	 * byte数组转long
	 * @param bytes 8位的byte数组
	 * @param littleEndian 是否是小端模式
	 * @return
	 * @throws Exception 
	 */
	public static long bytesToLong(byte[] bytes, boolean littleEndian) throws Exception {
		if(bytes.length != 8) {
			throw new Exception("参数错误，无法解析。");
		}
		ByteBuffer buffer = ByteBuffer.wrap(bytes,0,8);
		if(littleEndian){
		    // ByteBuffer.order(ByteOrder) 方法指定字节序,即大小端模式(BIG_ENDIAN/LITTLE_ENDIAN)
		    // ByteBuffer 默认为大端(BIG_ENDIAN)模式 
		    buffer.order(ByteOrder.LITTLE_ENDIAN);
		}
		return buffer.getLong();
    }
	
	/**
	 * int转byte数组  ,小端
	 * @param num
	 * @return
	 */
    public static byte[] intToBytes_Little(int num){  
        byte[] result = new byte[4];  
        result[0] = (byte)((num >>> 0) & 0xff);
        result[1] = (byte)((num >>> 8)& 0xff );  
        result[2] = (byte)((num >>> 16) & 0xff );  
        result[3] = (byte)((num >>> 24) & 0xff );  
        return result;  
    }
	
	/**
	 * int转byte数组 ,大端
	 * @param num
	 * @return
	 */
    public static byte[] intToBytes_Big(int num){  
        byte[] result = new byte[4];  
        result[0] = (byte)((num >>> 24) & 0xff);
        result[1] = (byte)((num >>> 16)& 0xff );  
        result[2] = (byte)((num >>> 8) & 0xff );  
        result[3] = (byte)((num >>> 0) & 0xff );  
        return result;  
    }
    
    /**
     * byte数组转int,小端
     * @param bytes
     * @return
     */
    public static int bytesToInt_Little(byte[] bytes){  
        int result = 0;  
        if(bytes.length == 4){  
            int a = (bytes[0] & 0xff) << 0;
            int b = (bytes[1] & 0xff) << 8;  
            int c = (bytes[2] & 0xff) << 16;  
            int d = (bytes[3] & 0xff) << 24;  
            result = a | b | c | d;  
        }  
        return result;  
    }
      
    /**
     * byte数组转int,大端
     * @param bytes
     * @return
     */
    public static int bytesToInt_Big(byte[] bytes){  
        int result = 0;  
        if(bytes.length == 4){  
            int a = (bytes[0] & 0xff) << 24;
            int b = (bytes[1] & 0xff) << 16;  
            int c = (bytes[2] & 0xff) << 8;  
            int d = (bytes[3] & 0xff) << 0;  
            result = a | b | c | d;  
        }  
        return result;  
    }  
    
    /**
     * byte数组转十六进制
     * @param bytes
     * @return
     */
    public static String bytesToHex(byte[] bytes) {
        StringBuilder buf = new StringBuilder(bytes.length * 2);
        for(byte b : bytes) { // 使用String的format方法进行转换
            buf.append(String.format("%02x", new Integer(b & 0xff)));
        }

        return buf.toString();
    }
    
    /**
     * 十六进制转byte数组
     * @param str
     * @return
     */
    public static byte[] hexToBytes(String str) {
        if(str == null || str.trim().equals("")) {
            return new byte[0];
        }
        byte[] bytes = new byte[str.length() / 2];
        for(int i = 0; i < str.length() / 2; i++) {
            String subStr = str.substring(i * 2, i * 2 + 2);
            bytes[i] = (byte) Integer.parseInt(subStr, 16);
        }
        return bytes;
    }
}