package com.wjy.effective;

public enum Singleton {

    INSTANCE;

    private int numa;

    private int numb;

    public int add(int a,int b){

        numa=a;

        numb=b;

        return numa+numb;

    }

}

package com.wjy.effective;

public class TestSingleton {

    public static void main(String args[]){

        Singleton instance=Singleton.INSTANCE;

        int sum=instance.add(, );

        System.out.println("result is: "+(sum+));

    }

}

result is: