Java中byte、byte数组与int、long的转换详解

//byte 与 int 的相互转换 
public static byte intToByte(int x) { 
 return (byte) x; 
} 
 
public static int byteToInt(byte b) { 
 //Java 总是把 byte 当做有符处理；我们可以通过将其和 0xFF 进行二进制与得到它的无符值 
 return b & 0xFF; 
} 

//测试 int 转 byte 
int int0 = 234; 
byte byte0 = intToByte(int0); 
System.out.println("byte0=" + byte0);//byte0=-22 
//测试 byte 转 int 
int int1 = byteToInt(byte0); 
System.out.println("int1=" + int1);//int1=234 

//byte 数组与 int 的相互转换 
public static int byteArrayToInt(byte[] b) { 
 return b[3] & 0xFF | 
  (b[2] & 0xFF) << 8 | 
  (b[1] & 0xFF) << 16 | 
  (b[0] & 0xFF) << 24; 
} 
 
public static byte[] intToByteArray(int a) { 
 return new byte[] { 
 (byte) ((a >> 24) & 0xFF), 
 (byte) ((a >> 16) & 0xFF), 
 (byte) ((a >> 8) & 0xFF), 
 (byte) (a & 0xFF) 
 }; 
} 

//测试 int 转 byte 数组 
int int2 = 1417; 
byte[] bytesInt = intToByteArray(int2); 
System.out.println("bytesInt=" + bytesInt);//bytesInt=[B@de6ced 
//测试 byte 数组转 int 
int int3 = byteArrayToInt(bytesInt); 
System.out.println("int3=" + int3);//int3=1417 

private static ByteBuffer buffer = ByteBuffer.allocate(8); 
//byte 数组与 long 的相互转换 
 public static byte[] longToBytes(long x) { 
 buffer.putLong(0, x); 
 return buffer.array(); 
 } 
 
 public static long bytesToLong(byte[] bytes) { 
 buffer.put(bytes, 0, bytes.length); 
 buffer.flip();//need flip 
 return buffer.getLong(); 
 } 

//测试 long 转 byte 数组 
long long1 = 2223; 
byte[] bytesLong = longToBytes(long1); 
System.out.println("bytes=" + bytesLong);//bytes=[B@c17164 
//测试 byte 数组 转 long 
long long2 = bytesToLong(bytesLong); 
System.out.println("long2=" + long2);//long2=2223 

import java.nio.ByteBuffer; 
 
 
public class Test { 
 
 private static ByteBuffer buffer = ByteBuffer.allocate(8); 
 
 public static void main(String[] args) { 
  
 //测试 int 转 byte 
 int int0 = 234; 
 byte byte0 = intToByte(int0); 
 System.out.println("byte0=" + byte0);//byte0=-22 
 //测试 byte 转 int 
 int int1 = byteToInt(byte0); 
 System.out.println("int1=" + int1);//int1=234 
  
  
  
 //测试 int 转 byte 数组 
 int int2 = 1417; 
 byte[] bytesInt = intToByteArray(int2); 
 System.out.println("bytesInt=" + bytesInt);//bytesInt=[B@de6ced 
 //测试 byte 数组转 int 
 int int3 = byteArrayToInt(bytesInt); 
 System.out.println("int3=" + int3);//int3=1417 
  
  
 //测试 long 转 byte 数组 
 long long1 = 2223; 
 byte[] bytesLong = longToBytes(long1); 
 System.out.println("bytes=" + bytesLong);//bytes=[B@c17164 
 //测试 byte 数组 转 long 
 long long2 = bytesToLong(bytesLong); 
 System.out.println("long2=" + long2);//long2=2223 
 } 
 
 
 //byte 与 int 的相互转换 
 public static byte intToByte(int x) { 
 return (byte) x; 
 } 
 
 public static int byteToInt(byte b) { 
 //Java 总是把 byte 当做有符处理；我们可以通过将其和 0xFF 进行二进制与得到它的无符值 
 return b & 0xFF; 
 } 
 
 //byte 数组与 int 的相互转换 
 public static int byteArrayToInt(byte[] b) { 
 return b[3] & 0xFF | 
  (b[2] & 0xFF) << 8 | 
  (b[1] & 0xFF) << 16 | 
  (b[0] & 0xFF) << 24; 
 } 
 
 public static byte[] intToByteArray(int a) { 
 return new byte[] { 
  (byte) ((a >> 24) & 0xFF), 
  (byte) ((a >> 16) & 0xFF), 
  (byte) ((a >> 8) & 0xFF), 
  (byte) (a & 0xFF) 
 }; 
 } 
 
 //byte 数组与 long 的相互转换 
 public static byte[] longToBytes(long x) { 
 buffer.putLong(0, x); 
 return buffer.array(); 
 } 
 
 public static long bytesToLong(byte[] bytes) { 
 buffer.put(bytes, 0, bytes.length); 
 buffer.flip();//need flip 
 return buffer.getLong(); 
 } 
 
} 

byte0=-22
int1=234
bytesInt=[B@de6ced
int3=1417
bytes=[B@c17164
long2=2223