Java十进制转为二进制

import java.util.*;

public class Test15 {
 public static void main(String[] args) {
  System.out.println(toBinary(32));
 }

 public static String toBinary(int a) {
  String str = "";
  Stack s = new Stack();
  while (a != 0) {
   s.push(a % 2);
   a = a / 2;
  }
  while (!s.empty()) {
   str += s.pop();
  }
  return str;
 }
}