单利模式

1、饿汉式

package com.company;

/**
 * 饿汉式
 * Created by dra on 2017/7/7.
 */
public class Person {


    private String name;

    private static final Person PERSON = new Person();

    private  Person(){}

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    /**
     * 获取单利
     * @return
     */
    public static Person getPerson(){
        return PERSON;
    }
}

2、懒汉式

package com.company;

/**
 * 懒汉式
 * Created by dra on 2017/7/7.
 */
public class Person2 {


    private String name;

    private static Person2 person;

    private Person2(){}

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    /**
     * 获取单利
     * @return
     */
    public static Person2 getPerson(){
        if (person == null){
            person= new Person2();
        }

        return person;
    }
}

3、双重检查

package com.company;

/**
 * 双重检查
 * Created by dra on 2017/7/7.
 */
public class Person2 {


    private String name;

    private static Person2 person;

    private Person2(){}

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    /**
     * 获取单利
     * @return
     */
    public static Person2 getPerson(){
        if (person== null){
            synchronized (Person2.class){
                if (person== null){
                    person= new Person2();
                }
            }
        }
        return person;
    }
}

转载于:https://www.jianshu.com/p/0dffbcb97d44