改用switch-case后，代码如下：

package com.java;

import java.util.Scanner;

public class TestTransform {

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

for(;;){

System.out.println(“请输入小于2的31次方的正整数：(輸入0結束程序)”);

int i = sc.nextInt();

if(i==0){

System.out.println(“程序结束！”);

break;

}else{

int num = 0;

if(i>=Math.pow(2, 0) && i

num = 1;

}else if(i>=Math.pow(2, 4) && i

num = 2;

}else if(i>=Math.pow(2, 8) && i

num = 3;

}else if(i>=Math.pow(2, 12) && i

num = 4;

}else if(i>=Math.pow(2, 16) && i

num = 5;

}else if(i>=Math.pow(2, 20) && i

num = 6;

}else if(i>=Math.pow(2, 24) && i

num = 7;

}else if(i>=Math.pow(2, 28) && i

num = 8;

}

switch(num){

case 8:

int i8 = i>>28 & 15;

String s8 = i8<=9 ? i8+”” : (char)(i8-10+’a’)+””;

System.out.print(s8);

case 7:

int i7 = i>>24 & 15;

String s7 = i7<=9 ? i7+”” : (char)(i7-10+’a’)+””;

System.out.print(s7);

case 6:

int i6 = i>>20 & 15;

String s6 = i6<=9 ? i6+”” : (char)(i6-10+’a’)+””;

System.out.print(s6);

case 5:

int i5 = i>>16 & 15;

String s5 = i5<=9 ? i5+”” : (char)(i5-10+’a’)+””;

System.out.print(s5);

case 4:

int i4 = i>>12 & 15;

String s4 = i4<=9 ? i4+”” : (char)(i4-10+’a’)+””;

System.out.print(s4);

case 3:

int i3 = i>>8 & 15;

String s3 = i3<=9 ? i3+”” : (char)(i3-10+’a’)+””;

System.out.print(s3);

case 2:

int i2 = i>>4 & 15;

String s2 = i2<=9 ? i2+”” : (char)(i2-10+’a’)+””;

System.out.print(s2);

case 1:

int i1 = i & 15;

String s1 = i1<=9 ? i1+”” : (char)(i1-10+’a’)+””;

System.out.println(s1);

}

}

}

}

}

自己写的，欢迎各位友友交流挑错，赐教调优方法！