javadouble转byte数组_Java基本类型与byte数组的转换

Java基本类型与byte数组之间相互转换&＃xff1a;

package cn.teaey.utils;

import java.nio.charset.Charset;

public class ByteUtil

{

public static byte[] getBytes(short data)

{

byte[] bytes &＃61; new byte[2];

bytes[0] &＃61; (byte) (data & 0xff);

bytes1 &＃61; (byte) ((data & 0xff00) >> 8);

return bytes;

}

public static byte[] getBytes(char data)

{

byte[] bytes &＃61; new byte[2];

bytes[0] &＃61; (byte) (data);

bytes[1] &＃61; (byte) (data >> 8);

return bytes;

}

public static byte[] getBytes(int data)

{

byte[] bytes &＃61; new byte[4];

bytes[0] &＃61; (byte) (data & 0xff);

bytes[1] &＃61; (byte) ((data & 0xff00) >> 8);

bytes[2] &＃61; (byte) ((data & 0xff0000) >> 16);

bytes[3] &＃61; (byte) ((data & 0xff000000) >> 24);

return bytes;

}

public static byte[] getBytes(long data)

{

byte[] bytes &＃61; new byte[8];

bytes[0] &＃61; (byte) (data & 0xff);

bytes[1] &＃61; (byte) ((data >> 8) & 0xff);

bytes[2] &＃61; (byte) ((data >> 16) & 0xff);

bytes[3] &＃61; (byte) ((data >> 24) & 0xff);

bytes[4] &＃61; (byte) ((data >> 32) & 0xff);

bytes[5] &＃61; (byte) ((data >> 40) & 0xff);

bytes[6] &＃61; (byte) ((data >> 48) & 0xff);

bytes[7] &＃61; (byte) ((data >> 56) & 0xff);

return bytes;

}

public static byte[] getBytes(float data)

{

int intBits &＃61; Float.floatToIntBits(data);

return getBytes(intBits);

}

public static byte[] getBytes(double data)

{

long intBits &＃61; Double.doubleToLongBits(data);

return getBytes(intBits);

}

public static byte[] getBytes(String data, String charsetName)

{

Charset charset &＃61; Charset.forName(charsetName);

return data.getBytes(charset);

}

public static byte[] getBytes(String data)

{

return getBytes(data, "GBK");

}

public static short getShort(byte[] bytes)

{

return (short) ((0xff & bytes[0]) | (0xff00 & (bytes[1] <<8)));

}

public static char getChar(byte[] bytes)

{

return (char) ((0xff & bytes[0]) | (0xff00 & (bytes[1] <<8)));

}

public static int getInt(byte[] bytes)

{

return (0xff & bytes[0]) | (0xff00 & (bytes[1] <<8)) | (0xff0000 & (bytes[2] <<16)) | (0xff000000 & (bytes[3] <<24));

}

public static long getLong(byte[] bytes)

{

return(0xffL & (long)bytes[0]) | (0xff00L & ((long)bytes[1] <<8)) | (0xff0000L & ((long)bytes[2] <<16)) | (0xff000000L & ((long)bytes[3] <<24))

| (0xff00000000L & ((long)bytes[4] <<32)) | (0xff0000000000L & ((long)bytes[5] <<40)) | (0xff000000000000L & ((long)bytes[6] <<48)) | (0xff00000000000000L & ((long)bytes[7] <<56));

}

public static float getFloat(byte[] bytes)

{

return Float.intBitsToFloat(getInt(bytes));

}

public static double getDouble(byte[] bytes)

{

long l &＃61; getLong(bytes);

System.out.println(l);

return Double.longBitsToDouble(l);

}

public static String getString(byte[] bytes, String charsetName)

{

return new String(bytes, Charset.forName(charsetName));

}

public static String getString(byte[] bytes)

{

return getString(bytes, "GBK");

}

public static void main(String[] args)

{

short s &＃61; 122;

int i &＃61; 122;

long l &＃61; 1222222;

char c &＃61; &＃39;a&＃39;;

float f &＃61; 122.22f;

double d &＃61; 122.22;

String string &＃61; "我是好孩子";

System.out.println(s);

System.out.println(i);

System.out.println(l);

System.out.println(c);

System.out.println(f);

System.out.println(d);

System.out.println(string);

System.out.println("**************");

System.out.println(getShort(getBytes(s)));

System.out.println(getInt(getBytes(i)));

System.out.println(getLong(getBytes(l)));

System.out.println(getChar(getBytes(c)));

System.out.println(getFloat(getBytes(f)));

System.out.println(getDouble(getBytes(d)));

System.out.println(getString(getBytes(string)));

}

}

java的基本类型存储长度都是固定的&＃xff0c;不因机器的不同而不同&＃xff0c;因此使java拥有了良好的移植性。

最近在做项目时&＃xff0c;需要在一个变量里存放16位长的二进制数字&＃xff0c;查看上表可知short类型正好符合需要。

但是因为java中的数字类型都是有符号的&＃xff0c;因此short类型的第一位被用于表示符号&＃xff0c;实际存储长度只有15位&＃xff0c;

即&＃xff0d;7FFF&＃xff0d;&＃xff0b;7FFF。那如果要存放&＃xff0b;7FFF&＃xff0d;&＃xff0b;FFFF的数字该怎么办呢&＃xff1f;只有采取变通的办法&＃xff0c;采用变换算法。我们可以利用&＃xff0d;7FFF&＃xff0d;&＃xff0d;0001来存放大于7FFF的数字。转换公式为&＃xff0d;(FFFF&＃xff0d;X)&＃xff0d;1。由于有了符号&＃xff0c;所以&＃xff0b;0000和&＃xff0d;0000是相等的&＃xff0c;所以比无符号数少了1个数字&＃xff0c;所以要在公式里减1&＃xff0c;由于这个问题&＃xff0c;用这个方法我们就不能存放&＃xff0b;8000了。

用这个方法可以基本满足我们的需要&＃xff0c;如有特殊需要&＃xff0c;如要存储&＃xff0b;8000&＃xff0c;那只有采取别的办法了。