Java - 两个类互相组合嵌套引用会爆炸吗？

Posted 2021-11-08 程序员牧码

Demo3.java 

package tech.luxsun.interview.luxinterviewstarter.demo;

import java.time.LocalDateTime;

public class Demo3 {
    private String sex;
    private String name;
    private Demo2 demo2;

    public Demo3(String sex, String name) {
        this.sex = sex;
        this.name = name;
    }

    public Demo3() {
    }

    public Demo2 getDemo2() {
        return demo2;
    }

    public void setDemo2(Demo2 demo2) {
        this.demo2 = demo2;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getName() {
        return name;
    }

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

    @Override
    public String toString() {
        return "Demo3{" +
                "sex='" + sex + '\\'' +
                ", name='" + name + '\\'' +
                ", demo2=" + demo2 +
                '}';
    }
}

Demo2.java

package tech.luxsun.interview.luxinterviewstarter.demo;

public class Demo2 {
    private String sex;
    private String name;
    private Demo3 demo3;

    public Demo2() {
    }

    public Demo3 getDemo3() {
        return demo3;
    }

    public void setDemo3(Demo3 demo3) {
        this.demo3 = demo3;
    }

    public Demo2(String sex, String name) {
        this.sex = sex;
        this.name = name;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getName() {
        return name;
    }

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

    public static void main(String[] args) {
        Demo2 demo2 = new Demo2();
        demo2.setName("Bob");
        demo2.setSex("男");

        Demo3 demo3 = new Demo3();
        demo3.setName("Alice");
        demo3.setSex("女");

        demo2.setDemo3(demo3);
        demo3.setDemo2(demo2);

        System.out.println(demo2.toString());
        System.out.println(demo3.getDemo2());
    }

    @Override
    public String toString() {
        return "Demo2{" +
                "sex='" + sex + '\\'' +
                ", name='" + name + '\\'' +
                ", demo3=" + demo3 +
                '}';
    }
}

• 目前 2 个 Demo 都重写了 toString，输出结果

Exception in thread "main" java.lang.StackOverflowError
	at java.lang.StringBuilder.append(StringBuilder.java:136)
	at tech.luxsun.interview.luxinterviewstarter.demo.Demo2.toString(Demo2.java:58)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
	at tech.luxsun.interview.luxinterviewstarter.demo.Demo3.toString(Demo3.java:44)
	at java.lang.String.valueOf(String.java:2994)
	at java.lang.StringBuilder.append(StringBuilder.java:131)
    ……

• 注释掉其中 1 个 Demo toString，输出结果

Demo2{sex='男', name='Bob', demo3=tech.luxsun.interview.luxinterviewstarter.demo.Demo3@19469ea2}
Demo2{sex='男', name='Bob', demo3=tech.luxsun.interview.luxinterviewstarter.demo.Demo3@19469ea2}