Java中如何使某个类的对象唯一性，只能创建一个对象

方法一、

对象唯一性一般能想到工厂模式，单例模式，我们这里介绍一下举例懒汉法。

package com.liuyanzhao;class Student {    private String name;    public void setName(String name) {        this.name = name;    }    public String getName() {        return name;    }    private Student() {    }    private static Student s = new Student();    public static Student getInstance() {        return s;    }}public class Test {    public static void main(String[] args) {        Student s1 = Student.getInstance();        Student s2 = Student.getInstance();        s1.setName("Tom");        s2.setName("Jerry");        System.out.println(s1.getName());//Jerry        System.out.println(s2.getName());//Jerry    }}

新建的两个对象s1,s2其实是一个对象

方法二、

通过计数器统计来创建对象

package com.liuyanzhao;class Teacher {    static int i=0;    private String name;    public void setName(String name) {        this.name = name;    }    public String getName() {        return name;    }    private Teacher() {    }    public static Teacher newTeacher() {        Teacher.i++;        if(Teacher.i>1){            return null;        }        return new Teacher();    }}public class Test1 {    public static void main(String[] args) {        Teacher t = Teacher.newTeacher();        Teacher t1 = Teacher.newTeacher();        t.setName("Tom");        //t1.setName("Jerry");        System.out.println(t.getName());        //System.out.println(t1.getName());    }}

如上 只能创建一个对象，否则会报错。

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