二进制中1的个数

public class 面试题10_二进制中1的个数 {
	public static void main(String[] args) {
//		System.out.println(Integer.toBinaryString(13));
//		System.out.println(Integer.toBinaryString(12));
//		System.out.println(Integer.toBinaryString(13&12));
		//countNum0(-156);
		countNum1(-2147483648);
		System.out.println(Integer.toBinaryString(-2147483648));
		//System.out.println(12&11);
	}
	//推荐解法
	public static void countNum(int n){
		int count=0;
		while(n!=0){
			count++;
			n=n&(n-1);
		}
		System.out.println(count);
	}
	public static void countNum0(int n){
		int count=0;
		String str=Integer.toBinaryString(n);
		char[] chs=str.toCharArray();
		for (int i = 0; i < str.length(); i++) {
			if(chs[i]=='1'){
				count++;
			}
		}
		System.out.println(count);
	}
	public static void  countNum1(int n){
		int count=0;
		for (int i = 0; i < 32; i++) {
			if((n&1)==1){
				count++;
			}
			System.out.println(count);
			n=n>>1;
		}
		System.out.println(count);
	}
	public static void  countNum2(int n){
		int count=0;
		int flag=1;
		for (int i = 0; i < 32; i++) {
			//System.out.println(n&flag);
			if((n&flag)!=0){
				count++;
			}
			flag=flag<<1;
		}
		System.out.println(count);
	}
}