[Java知识库]单例设计模式之饿汉式与懒汉式

饿汉式步骤：

class Bank{
    //1.私有化构造器
    private Bank(){

    }
    //2.内部创建类的对象
    //4.要求此对象也必须声明为静态
    private static Bank instance=new Bank();
    //3.提供公共的静态的方法，返回类的对象
    public static Bank getInstance(){
        return instance;
    }
}
public class SingletonTest {
    public static void main(String[] args) {
        Bank bank1=Bank.getInstance();
        Bank bank2=Bank.getInstance();
        System.out.println(bank1==bank2);
    }

}

懒汉式步骤：

public class SingletonTest2 {
    public static void main(String[] args) {
        Order order=Order.getInstance();
        Order order1=Order.getInstance();
        System.out.println(order==order1);
    }
}
class Order{
    //1.私有化构造器
    private Order(){

    }
    //2.内部创建类的对象
    //4.要求此对象也必须声明为静态
   private static Order instance=null;

    //3.提供公共的静态的方法，返回类的对象
    public static Order getInstance(){
        if (instance==null){
            instance=new Order();
        }
        return instance;
    }
}