Java –将byte []转换为int，反之亦然

一时失言乱红尘 2023-02-15 01:28 3阅读 0赞

在Java中，我们可以使用`ByteBuffer`将`int`转换为`byte[]` ，反之亦然。

`int`到`byte[]`

int num = 1;
      // int need 4 bytes, default ByteOrder.BIG_ENDIAN
      byte[] result =  ByteBuffer.allocate(4).putInt(number).array();

`byte[]`到`int`

byte[] byteArray = new byte[] {00, 00, 00, 01};
      int num = ByteBuffer.wrap(bytes).getInt();

## 1. int到byte \[\] ##

这个Java示例将一个`int`转换为一个字节数组，并以十六进制格式打印它。

IntToByteArrayExample.java

package com.mkyong.nio;
    
    import java.nio.ByteBuffer;
    
    public class IntToByteArrayExample {
    
        public static void main(String[] args) {
    
            int num = 1;
            byte[] result = convertIntToByteArray(num);
    
            System.out.println("Input            : " + num);
            System.out.println("Byte Array (Hex) : " + convertBytesToHex(result));
    
        }
    
        // method 1, int need 4 bytes, default ByteOrder.BIG_ENDIAN
        public static byte[] convertIntToByteArray(int value) {
            return  ByteBuffer.allocate(4).putInt(value).array();
        }
    
        // method 2, bitwise right shift
        public static byte[] convertIntToByteArray2(int value) {
            return new byte[] {
                    (byte)(value >> 24),
                    (byte)(value >> 16),
                    (byte)(value >> 8),
                    (byte)value };
        }
    
        public static String convertBytesToHex(byte[] bytes) {
            StringBuilder result = new StringBuilder();
            for (byte temp : bytes) {
                result.append(String.format("%02x", temp));
            }
            return result.toString();
        }
    
    }

输出量

Terminal

Input            : 1
    Byte Array (Hex) : 00000001

## 2. byte \[\]转换为int ##

ByteArrayToIntExample.java

package com.mkyong.nio;
    
    import java.nio.ByteBuffer;
    
    public class ByteArrayToIntExample {
    
        public static void main(String[] args) {
    
            // byte = -128 to 127
            byte[] byteArray = new byte[] {00, 00, 00, 01};
    
            int result = convertByteArrayToInt2(byteArray);
    
            System.out.println("Byte Array (Hex) : " + convertBytesToHex(byteArray));
            System.out.println("Result           : " + result);
    
        }
    
        // method 1
        public static int convertByteArrayToInt(byte[] bytes) {
            return ByteBuffer.wrap(bytes).getInt();
        }
    
        // method 2, bitwise again, 0xff for sign extension
        public static int convertByteArrayToInt2(byte[] bytes) {
            return ((bytes[0] & 0xFF) << 24) |
                    ((bytes[1] & 0xFF) << 16) |
                    ((bytes[2] & 0xFF) << 8) |
                    ((bytes[3] & 0xFF) << 0);
        }
    
        public static String convertBytesToHex(byte[] bytes) {
            StringBuilder result = new StringBuilder();
            for (byte temp : bytes) {
                result.append(String.format("%02x", temp));
            }
            return result.toString();
        }
    
    }

输出量

Terminal

Byte Array (Hex) : 00000001
    Result           : 1

## 参考文献 ##

*  Java –将字节转换为无符号字节
 *  [字节缓冲区JavaDoc][JavaDoc]
 *  [value＆0xff在Java中有什么作用？][value_0xff_Java]

标签： [0xff][] [ByteBuffer][] [字节][Link 1] [转换][Link 2] [Java][]

> 翻译自: [https://mkyong.com/java/java-convert-byte-to-int-and-vice-versa/][https_mkyong.com_java_java-convert-byte-to-int-and-vice-versa]

[JavaDoc]: https://docs.oracle.com/javase/7/docs/api/java/nio/ByteBuffer.html
[value_0xff_Java]: https://stackoverflow.com/questions/11380062/what-does-value-0xff-do-in-java
[0xff]: https://mkyong.com/tag/0xff/
[ByteBuffer]: https://mkyong.com/tag/bytebuffer/
[Link 1]: https://mkyong.com/tag/bytes/
[Link 2]: https://mkyong.com/tag/convert/
[Java]: https://mkyong.com/tag/java/
[https_mkyong.com_java_java-convert-byte-to-int-and-vice-versa]: https://mkyong.com/java/java-convert-byte-to-int-and-vice-versa/