1、long與byte之間的轉換

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) {
        return 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 static void main(String[] args) {
        int num = 129;
        System.out.println("測試的int值為:" + num);

        byte[] int2bytes = Utilities.int2Bytes(num);
        System.out.printf("int轉成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轉行成int: " + bytes2int);

        byte int2OneByte = Utilities.int2OneByte(num);
        System.out.println("int轉行成one byte: " + int2OneByte);

        int oneByte2Int = Utilities.oneByte2Int(int2OneByte);
        System.out.println("one byte轉行成int: " + oneByte2Int);
        System.out.println();

        long longNum = 100000;
        System.out.println("測試的long值為：" + longNum);

        byte[] long2Bytes = Utilities.long2Bytes(longNum);
        System.out.printf("long轉行成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轉行成long: " + bytes2Long);
    }
}
 

2、int和byte轉換

package com.chargedot.util;

/**
 * @Author：caoj
 * @Description：
 * @Data：Created in 2018/5/14
 */
public class ByteUtil {

    public static int bytesToInt(byte[] data, int pos, int len) {

        int value = 0;
        for (int i = len - 1; i >= 0; i--) {
            int shift = i * 8;
            value += (data[pos + i] & 0x000000FF) << shift;
        }
        return value;
    }

    public static int byte2int(byte[] res) {
        int targets = (res[0] & 0xff) | ((res[1] << 8) & 0xff00) // | 表示安位或
                | ((res[2] << 24) >>> 8) | (res[3] << 24);
        return targets;
    }

    public static void fillBytes(byte[] dst, int pos, int value, int len) {
        for (int i = 0; i < len; i++) {
            dst[pos + i] = (byte) (value & 0xff);
            value = (value >> 8);
        }
    }

    public static void fillBytes(byte[] dst, int pos, String value) {
        for (int i = 0; i < value.length(); i++) {
            dst[pos + i] = (byte) (value.charAt(i) & 0xff);
        }
    }

    public static byte[] intToBytes(int value) {
        byte[] b = new byte[4];
        b[0] = (byte) (value & 0xff);
        b[1] = (byte) (value >> 8 & 0xff);
        b[2] = (byte) (value >> 16 & 0xff);
        b[3] = (byte) (value >> 24 & 0xff);
        return b;
    }

    public static byte[] intToBytes3(int value) {
        byte[] b = new byte[3];
        b[0] = (byte) (value & 0xff);
        b[1] = (byte) (value >> 8 & 0xff);
        b[2] = (byte) (value >> 16 & 0xff);
        return b;
    }

    public static byte[] toHH2(int n) {
        byte[] b = new byte[2];
        b[0] = (byte) (n & 0xff);
        b[1] = (byte) (n >> 8 & 0xff);
        return b;
    }

    //10進位制轉16進位制字串
    public static String decimalToHex(int decimal) {
        String hex = "";
        while(decimal != 0) {
            int hexValue = decimal % 16;
            hex = toHexChar(hexValue) + hex;
            decimal = decimal / 16;
        }
        return  hex;
    }

    //將0~15的十進位制數轉換成0~F的十六進位制數
    public static char toHexChar(int hexValue) {
        if(hexValue <= 9 && hexValue >= 0)
            return (char)(hexValue + '0');
        else
            return (char)(hexValue - 10 + 'A');
    }

}