C1_26_BinaryOneCounter.java

package com.interview.algorithms.general;

import com.interview.utils.ConsoleReader;

/**
 * Chapter 2.1 Count the amout of '1's in an integer's binary form
 * @author zouzhile (zouzhile@gmail.com)
 *
 */
public class C1_26_BinaryOneCounter {
    public static int countByMode2(int value){
        int count = 0;
        while(value != 0){
            if(value % 2 == 1) count++;
            value = value / 2;
        }
        return count;
    }

	public static int countByBitOp(int value){
		int amount = 0;
		while (value != 0){
			amount += value & 1;
			value >>>= 1;
		}
		return amount;
	}

    public static int count(int value){
        int amount = 0;
        while(value != 0){
            value = value & (value - 1);
            amount++;
        }
        return amount;
    }
	
	public static void main(String[] args) {
		System.out.println("Binary One Counter");
		System.out.println("========================================================================");
		ConsoleReader reader = new ConsoleReader();
		System.out.print("Plz input an integer : ");
        int value = reader.readInt();
        System.out.println("The binary form of the input integer: " + Integer.toBinaryString(value));

        C1_26_BinaryOneCounter counter = new C1_26_BinaryOneCounter();
        int amount = counter.count(value);
        System.out.println("The amount of '1' is : " + amount);
	}

}