java 数字转化成字节存储算法

http://jlins.iteye.com/blog/1062928

package com;

import java.io.File;

import java.io.FileOutputStream;
import java.io.IOException;

public class TestByte {

	/**
	 * ip转化成4个字节进行存储,然后再把四个字节转换成byte
	 */
	public static void ipTobyte()
	{
	   String ip="222.168.205.83";	
	   String[] ips = ip.split("\\.");
	   int ip1 = Integer.valueOf(ips[0]);
	   int ip2 = Integer.valueOf(ips[1]);
	   int ip3 = Integer.valueOf(ips[2]);
	   int ip4 = Integer.valueOf(ips[3]);
	   System.out.println(ip1);
	   System.out.println(ip2);
	   System.out.println(ip3);
	   System.out.println(ip4);
	   byte b1 = (byte)ip1;
	   byte b2 = (byte)ip2;
	   byte b3 = (byte)ip3;
	   byte b4 = (byte)ip4;
	   
	   System.out.println(b1);
	   System.out.println(b2);
	   System.out.println(b3);
	   System.out.println(b4);
	   // int 转byte之后 操作127的数字将全部变成负数形式,如果想转成原来的 int值  直接 & 0xFF
	   System.out.println(b1 & 0xFF);
	   System.out.println(b2 & 0xFF);
	   System.out.println(b3 & 0xFF);
	   System.out.println(b4 & 0xFF);
	   
	}
	public static void byteToIP()
	{
		
	}
	/**
	 * long -> 4位字节 -> long 
	 * 主要是做了一个数据压缩算法
	 * 比如说一个ip可以直接存储成4个字节
	 */
	public static void numToBinaryString()
	{
		//源数字
		long num = 98786657;
		//转化成二进制串
		String binary = Long.toBinaryString(num);
		System.out.println(binary);
	    int length = 32-binary.length();
	    //补充到32位
		for(int i=0;i<length;i++)
		{
			binary = '0'+binary;
		}
		System.out.println(binary);
		System.out.println(binary.length());
		//分割成四个字节 (一个字节8位)
		String b1 = binary.substring(0, 8);
		String b2 = binary.substring(8, 16);
		String b3 = binary.substring(16, 24);
		String b4 = binary.substring(24, 32);
		System.out.println(b1);
		System.out.println(b2);
		System.out.println(b3);
		System.out.println(b4);
		//8位转化成一个字节
		int a1 = Integer.valueOf(b1, 2);
		int a2 = Integer.valueOf(b2, 2);
		int a3 = Integer.valueOf(b3, 2);
		int a4 = Integer.valueOf(b4, 2);
		System.out.println(a1);
		System.out.println(a2);
		System.out.println(a3);
		System.out.println(a4);
		byte c1 = (byte)a1;
		byte c2 = (byte)a2;
		byte c3 = (byte)a3;
		byte c4 = (byte)a4;
		System.out.println(c1);
		System.out.println(c2);
		System.out.println(c3);
		System.out.println(c4);
		
		//把字节转化成long 
		long ret = 0;
		ret |= c4 & 0xFF;
		ret |= (c3<<8) & 0xFF00;
		ret |= (c2<<16) & 0xFF0000;
		ret |= (c1<<24) & 0xFF000000;
		
		System.out.println(ret);
		// Integer.toBinaryString(c4&0xFF);
	//	System.out.println();
		
	}
	/**
	 * 把字节写入文件,看看是啥效果
	 * @throws IOException
	 */
	public static void writeByteToFile() throws IOException
	{
		File file = new File("a.txt");
		FileOutputStream fis = new FileOutputStream(file);
		fis.write(-106);
		fis.write(-38);
		fis.write(0);
		fis.write(11);
		fis.flush();
		System.out.println(file.getAbsolutePath());
	}
	public static void main(String[] args) throws IOException
	{
	//	TestByte.writeByteToFile();
	//	TestByte.numToBinaryString();
		TestByte.ipTobyte();
	}
}