java面试每日一题9

题目：判断一个数是否是2的方次幂

public class Power {
    public static void main(String [] args) throws NumberFormatException, IOException{
        System.out.println("请输入一个数：");
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        int i=Integer.parseInt(br.readLine());
        isPower(i);
    }

private static void isPower(int num){
    if(((num - 1) & num) == 0){
        System.out.println("是方次幂");
    }else{
        System.out.println("不是方次幂");
    }   
　}
}

private static void isPower(int num){
    boolean flag=false;
    for(int i=num;i>0;i--){
        int a = num/2;
        int b=num%2;
        num=a;
        System.out.println("num是"+num+"取余是"+b);
            if(num>2){
                System.out.println(88);
            }
            if(num<=2){
            int c=(num*2+b)%2;
                if(c==0){
                    flag=true;
                }else{
                    flag=false;
                }
            break;
        }
    }
    if(flag==true){
        System.out.println("该数是2的方次幂");
    }
    if(flag==false){
        System.out.println("该数不是2的方次幂");
    }
    
}