java中十进制转换为二进制、八进制和十六进制

public   static   String   toBinaryString(int   i)

public   static   String   toHexString(int   i)

public   static   String   toOctalString(int   i)

例如：计算一个字节中置为1的个数。

public class theNumberOfOne {/*** @param args*/public static void main(String[] args) {// TODO Auto-generated method stubbyte s = 0x7F;int count = countNumberOne(s);System.out.println(count);}public static int countNumberOne(byte s){int count = 0;System.out.println(s);String str =Byte.toString(s); //s+"";//str = Integer.toBinaryString(Integer.parseInt(str))+"";System.out.println(str);for(int i=0;i<7;i++){if((str.substring(i,i+1)).equals("1")){count++;}}return count;}}