java - 如何为两个互相指向的对象编写 toString

Question

class A {
    String one;
    String two;
    B bRef;
    Collection<B> bCollRef;

    A(String one, String two)
    {
        this.one = one;
        this.two = two;
    }

    //setters for bRef and bCollRef;
}

class B {
    String three;
    A a;

    B(String three)
    {
        this.three = three;
    }

    //setter for a
}

A a1 = new A(...);
A a2 = new A(...);
a1.setbRef(new B(str,a2));
a2.setbCollRef(new B(str,a1));

a2 就像 a1 的子级，a1 是 a2 的父级。为这些类编写 toString 方法并避免 stackoverflow 错误的最佳方法是什么。

Answer 1

假设您有一个用于 B 中的 A 引用的公共(public)访问器，这将起作用

class A {
    String one;
    String two;
    B bRef;
    Collection<B> bCollRef;

    A(String one, String two)
    {
        this.one = one;
        this.two = two;
    }

    //setters for bRef and bCollRef;

    @Override
    public void toString(){

        if(bRef.geta() == this)
            //you have a circular reference, dont step into it(don't call the next toString() method) and you won't stackoverflow here
        else
            //no circular reference, no problems here, tostring it as you will

    }
}

现在，如何编写 toString() 方法取决于您希望如何将对象转换为字符串...这个简单的 if 语句将保护您免受循环引用的影响。如果您有更多可能使事情复杂化的引用，我建议您退后一步并重新思考您是如何做事的，您的对象不应该需要看到所有其他对象。

如果您确实有高阶循环引用情况，并且有引用b1和b2，例如a1 -> b1 -> a2 -> b2 -> a1 你需要编写这样的代码..但在实践中你需要非常小心空引用:

    @Override
    public String toString(){
        //do tostring stuff on current object
        A nextA = bRef.geta(); 
        //do tostring stuff on next stuff

        while(nextA != this){
             nextA = nextA.getbRef.getA();
             //unravel the references until you come around full-circle
        }

    }