饿汉式

public class Main {

public static void main(String[] args) {
    Singleton s1 = Singleton.getInstance();
    Singleton s2 = Singleton.getInstance();
    System.out.println(s1 == s2);
}

}

class Singleton {

private static Singleton instance = new Singleton();

private Singleton() {

}

//write your code here......
 
public static Singleton getInstance() {
    return instance;
}

}