java byte 与 binary 转换

  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();@Testpublic 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);}@Testpublic 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);}@Testpublic 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);}@Testpublic void float2byteTest(){float f = 233344.233444f;byte[] bytes = test.float2byte(f);float j = test.byte2float(bytes);Assert.assertEquals(f, j);}@Testpublic void double2byteTest(){double d = 233344.233444;byte[] bytes = test.double2byte(d);double j = test.byte2double(bytes);Assert.assertEquals(d, j);}}