java - 这在 Java 中 - 线程 "main"java.lang.StackOverflowError 中的异常

Question

为什么我会收到 stackoverflow 错误？

我的类(class)-

public class Tester {

int id;

 Tester(int id){
  this.id = id;
 }

 public String toString(){

  String rep = "Hex: " + this + ", Id: " + this.id;
  return rep;
 }

}

主要方法-

class Driver{

    public static void main(String [] args){

        Tester t = new Tester(123);
        System.out.println(t);

    }

}

错误-

Exception in thread "main" java.lang.StackOverflowError
    at java.lang.String.length(Unknown Source)
    at java.lang.AbstractStringBuilder.append(Unknown Source)
    at java.lang.StringBuilder.append(Unknown Source)
    at java.lang.StringBuilder.<init>(Unknown Source)
    at com.examscam.model.Tester.toString(Tester.java:13)
    at java.lang.String.valueOf(Unknown Source)
    at java.lang.StringBuilder.append(Unknown Source)

---------REPEAT !!!

Answer 1

因为

"Hex: " + this

相当于

"Hex: " + this.toString()

并且您是从 toString() 执行此操作的，因此 toString() 调用自身，后者调用自身，后者调用自身...