eclipse没问题，leetcode 1不能通过，超出int最大值了，但是怎么转无符号？
/*Write a function that takes an unsigned integer and returns the number of ’1‘ bits it has (also known as the Hamming weight).
For example, the 32-bit integer ’11‘ has binary representation 00000000000000000000000000001011, so the function should return 3.
*/
public static long reverseBits(int n) { long sum=0; List<Character> al=new ArrayList<Character>(); String str = Long.toBinaryString(n); char[] ch = str.toCharArray(); for(int i=0;i<32-ch.length;i++) al.add(‘0‘); for (int i = 0; i < ch.length; i++) al.add(ch[i]); System.out.println(al); for(int i=31;i>=0;i--) { if(al.get(i)==‘1‘) sum+=Math.pow(2,i);} return sum; }
原文：http://www.cnblogs.com/kydnn/p/4550664.html