CODEWITHSUNDEEP
java
Shivam Beohar
Shivam Beohar

Reputation: 83

StackOverFlowError at Runtime

When I run this code I am getting a StackOverFlowError at runtime. Why am I getting this Exception?

 class F{
    String name;
    int rollNo;
    F ref;

    F(String name,int rollNo){
        this.name = name;
        this.rollNo = rollNo;
        ref = this;
    }

    public static void main(String[] args){
        F f = new F("Shivam",138);
        System.out.println(f);
    }

    public String toString(){
        return name+" "+rollNo+" "+ref;
    }
}

This is the Exception I am getting:

Exception in thread "main" java.lang.StackOverflowError
    at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:449)
    at java.lang.StringBuilder.append(StringBuilder.java:136)
    at F.toString(F.java:20)
    at java.lang.String.valueOf(String.java:2994)
    at java.lang.StringBuilder.append(StringBuilder.java:131)
    at F.toString(F.java:20)
    at java.lang.String.valueOf(String.java:2994)
    at java.lang.StringBuilder.append(StringBuilder.java:131)
    at F.toString(F.java:20)
    at java.lang.String.valueOf(String.java:2994)

Upvotes: 1

Views: 120

Answers (3)

mcacorner
mcacorner

Reputation: 1274

Problem with overridden method toString() when you use ref it calling its toString() method and again same method call became recursive which causes the problem. You should use field of your class instead of same class object.

Upvotes: 1

adn.911
adn.911

Reputation: 1314

It's because you are self referencing using ref and printing in toString() which creates an endless recursion of toString() being called. Not sure why you need a self reference in the first place, you can just use this when needed. if you really need ref, you can remove it from toString() method and it should work.

Upvotes: 1

Syed Khalid Ahmed
Syed Khalid Ahmed

Reputation: 3232

System.out.println(f); // cause StackOverFlow  Exception

when this line executes toString() method called of f object. and see the implementation of toString()

public String toString(){
    return name+" "+rollNo+" "+ref;
}

In which you again concatenate the ref object so, toString method recursively calling infinitely. change implementation of toString to this.

public String toString(){
    return name+" "+rollNo;
}

Upvotes: 6

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