单列模式【饿汉式和懒汉式】

package com.linghu.single;
/**
 * 饿汉式
 * @author 令狐荣豪
 * @version 1.0
 */
public class SingleTon01 {
    public static void main(String[] args) {
//        Girlfriend instance = Girlfriend.getInstance();
//        System.out.println(instance);
        //饿汉式
        System.out.println(Girlfriend.n);//访问静态属性时，类的对象还是会被初始化创建，这就浪费了！
    }
}
class Girlfriend{
    private String name;
    public static int n=100;
    private static Girlfriend gf=new Girlfriend("小红");
    private Girlfriend(String name) {
        System.out.println("构造器。。。");
        this.name = name;
    }
    public static Girlfriend getInstance(){
        return gf;
    }
    @Override
    public String toString() {
        return "Girlfriend{" +
                "name='" + name + '\'' +
                '}';
    }
}

package com.linghu.single;
/**
 * 懒汉式
 * @author 令狐荣豪
 * @version 1.0
 */
public class SingleTon02 {
    public static void main(String[] args) {
        //访问静态属性的时候，对象不会被创建，不会浪费，需要的时候才会初始化创建对象
        System.out.println(Cat.n);
//        Cat instance = Cat.getInstance();
//        System.out.println(instance);
    }
}
class Cat{
    private String name;
   public static int n=100;
    private static Cat cat;
    private Cat(String name) {
        System.out.println("构造器调用...");
        this.name = name;
    }
    public static Cat getInstance(){
        if (cat==null){
            cat=new Cat("喵喵");
        }
        return cat;
    }
    @Override
    public String toString() {
        return "Cat{" +
                "name='" + name + '\'' +
                '}';
    }
}