java数值类型与二进制byte数组之间的转换

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在写通讯程序时，有时需要解析二进制数据流，可能会遇到java数值类型与二进制byte数组的类型转换问题。因此，笔者提供下面代码实例，供大家需要时参考。

import java.io.*;
/**
* java数值类型与二进制类型相互转换
* @author lijun
*
*/
public class MyTest {
/**
* int32转换为二进制（4个字节）
* @param i 待转换的整数
* @return 返回4字节二进制数
*/
public byte[] int2byte(int i){
byte[] res = new byte[4];
res[3] = (byte)i;
res[2] = (byte)(i>>>8);
res[1] = (byte)(i>>>16);
res[0] = (byte)(i>>>24);
return res;
}
/**
* 4字节二进制数转换为int32的整数
* @param bytes 4字节的二进制数
* @return int32整数
*/
public int byte2int(byte[] bytes){
int res = (((bytes[0]<<24)>>>24)<<24)|(((bytes[1]<<24)>>>24)<<16)|(((bytes[2]<<24)>>>24)<<8)|((bytes[3]<<24)>>>24);
return res;
}
/**
* int16整数转换二2字节的二进制数
* @param i int16整数
* @return 2字节的二进制数
*/
public byte[] int16Tobyte(int i){
byte[] res = new byte[2];
res[1] = (byte)i;
res[0] = (byte)(i>>>8);
return res;
}
/**
* 2字节的二进制数转换为int16整数
* @param bytes 2字节的二进制数
* @return int16整数
*/
public int byteToint16(byte[] bytes){
int res = ((bytes[0]<<8)|((bytes[1]<<24)>>>24));
return res;
}
/**
* 长整型long转换为8字节的二进制数
* @param l 长整型long
* @return 8字节的二进制数
*/
public byte[] long2byte(long l){
byte[] res = new byte[8];
res[7] = (byte)l;
res[6] = (byte)(l>>>8);
res[5] = (byte)(l>>>16);
res[4] = (byte)(l>>>24);
res[3] = (byte)(l>>>32);
res[2] = (byte)(l>>>40);
res[1] = (byte)(l>>>48);
res[0] = (byte)(l>>>56);
return res;
}
/**
* 8字节的二进制数转换为长整型long
* @param bytes 8字节的二进制数
* @return 长整型long
*/
public long byte2long(byte[] bytes){
long l0 = bytes[0];
long l1 = bytes[1];
long l2 = bytes[2];
long l3 = bytes[3];
long l4 = bytes[4];
long l5 = bytes[5];
long l6 = bytes[6];
long l7 = bytes[7];
long res = (l0<<56)|(((l1<<56)>>>56)<<48)|(((l2<<56)>>>56)<<40)|(((l3<<56)>>>56)<<32)|(((l4<<56)>>>56)<<24)|(((l5<<56)>>>56)<<16)|(((l6<<56)>>>56)<<8)|((l7<<56)>>>56);
return res;
}
/**
* 浮点型float转换为4字节的二进制数
* @param f 浮点数float
* @return 4字节的二进制数
*/
public byte[] float2byte(float f){
byte[] res = new byte[4];
int l = Float.floatToIntBits(f);
for(int i=3; i>=0; i--){
res[i] = new Integer(l).byteValue();
l >>= 8;
}
return res;
}
/**
* 4字节的二进制数转换为浮点数float
* @param bytes 4字节的二进制数
* @return 浮点数float
*/
public float byte2float(byte[] bytes){
int l = byte2int(bytes);
float res = Float.intBitsToFloat(l);
return res;
}
/**
* 双浮点数转换为8字节的二进制数
* @param d 双浮点数double
* @return 8字节的二进制数
*/
public byte[] double2byte(double d){
long l = Double.doubleToLongBits(d);
byte[] res = long2byte(l);
return res;
}
/**
* 8字节的二进制数转换为双浮点数
* @param bytes 8字节的二进制数
* @return 双浮点数double
*/
public double byte2double(byte[] bytes){
long l = byte2long(bytes);
double res = Double.longBitsToDouble(l);
return res;
}
public void test()throws Exception{
FileOutputStream fos = new FileOutputStream("d:/data.dat");
java.io.DataOutputStream dos = new DataOutputStream(fos);
double d = 233344.233444;
dos.writeDouble(d);
dos.close();
fos.close();
}
public static void main(String[] args)throws Exception{
System.out.println("begin write a int type to file:'c:/data.dat'");
new MyTest().test();
System.out.println("end write..");
}
}

以下为单元测试代码：

import junit.framework.Assert;

import org.junit.Test;

public class MyTestTest {
private MyTest test = new MyTest();
@Test
public void int2byteTest()
{
int i = -10101;
byte[] bytes = test.int2byte(i);
int j = test.byte2int(bytes);
Assert.assertEquals(i, j);
i = 10101;
bytes = test.int2byte(i);
j = test.byte2int(bytes);
Assert.assertEquals(i, j);
i = -0x1f1f1f;
bytes = test.int2byte(i);
j = test.byte2int(bytes);
Assert.assertEquals(i, j);
i = 0x1f1f1f;
bytes = test.int2byte(i);
j = test.byte2int(bytes);
Assert.assertEquals(i, j);
i = 0x1f1f1f1f;
bytes = test.int2byte(i);
j = test.byte2int(bytes);
Assert.assertEquals(i, j);
i = -0x1f1f1f1f;
bytes = test.int2byte(i);
j = test.byte2int(bytes);
Assert.assertEquals(i, j);
}

@Test
public void int16TobyteTest(){
int i = -0x01;
byte[] bytes = test.int16Tobyte(i);
int j = test.byteToint16(bytes);
Assert.assertEquals("-0x01",i, j);
i = 0x01;
bytes = test.int16Tobyte(i);
j = test.byteToint16(bytes);
Assert.assertEquals("0x01",i, j);
i = -0x0101;
bytes = test.int16Tobyte(i);
j = test.byteToint16(bytes);
Assert.assertEquals("-0x0101",i, j);
i = 0x0101;
bytes = test.int16Tobyte(i);
j = test.byteToint16(bytes);
Assert.assertEquals("0x0101",i, j);
}

@Test
public void long2byteTest(){
long l = -0x01;
byte[] bytes = test.long2byte(l);
long j = test.byte2long(bytes);
Assert.assertEquals("-0x01",l, j);
l = 0x01;
bytes = test.long2byte(l);
j = test.byte2long(bytes);
Assert.assertEquals("0x01",l, j);
l = -0x0101;
bytes = test.long2byte(l);
j = test.byte2long(bytes);
Assert.assertEquals("-0x0101",l, j);
l = -0x0101;
bytes = test.long2byte(l);
j = test.byte2long(bytes);
Assert.assertEquals("-0x0101",l, j);
}

@Test
public void float2byteTest()
{
float f = 233344.233444f;
byte[] bytes = test.float2byte(f);
float j = test.byte2float(bytes);
Assert.assertEquals(f, j);
}

@Test
public void double2byteTest(){
double d = 233344.233444;
byte[] bytes = test.double2byte(d);
double j = test.byte2double(bytes);
Assert.assertEquals(d, j);
}
}