Java overloading toString() method when array of class is given

Question

This is how you overload the toString() method:

public class Person extends Object {
    @Override
    public final String toString() {
        Gson gson = new GsonBuilder().serializeNulls().create();
        return (gson.toJson(this));
    }
}

In this example I get a JSON string when calling the toString() method of Person instead of the default string representation of an Object.

But what if I have an array of Person like:

Person[] persons = new Person[3];
System.out.println(persons.toString());

What do I have to do or which method(s) do I have to override in that case?

It is not possible, but you can use Arrays.toString(Object[] a); which will call the toString() method on each object in the array. — michal, Jun 06 '13 at 19:26
Why downvoting and requesting to close this question? I mean yes, there is another similar one but I could not find it because there are many ways to ask this question. Thanks for your help, I will use `Arrays.toString(Object[] a)`. — arminb, Jun 06 '13 at 19:36

greedybuddha · Answer 1 · 2013-06-06T19:30:13.517

2

You can't override the "array" version as their is no array version. What really happens is that the Array has a toString method which will be called.

If you had used a Java Collection as opposed to an Array, it would print out your Person#toString method 3 times as the Collection#toString iterates over each object in the collection.

edited Jun 06 '13 at 19:30

answered Jun 06 '13 at 19:25

greedybuddha

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It will call the Array toString method. – zw324 Jun 06 '13 at 19:25
That's what I said, "What really happens it that the Array has a toString method" – greedybuddha Jun 06 '13 at 19:26
You are right, but it does not try to call Person#toString. – zw324 Jun 06 '13 at 19:27
Actually this got me curious if it's possible to override the toString() method of an array variable using the reflection/instrumentation API. Probably not. – Piovezan Jun 06 '13 at 19:28
I was thinking about java collections, I revised my answer – greedybuddha Jun 06 '13 at 19:28

score 1 · Accepted Answer · answered Jun 06 '13 at 19:27

1

You cannot override default array's toString. If you want to convert an array of objects into the string, use Arrays.toString().

answered Jun 06 '13 at 19:27

tcb

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score 1 · Answer 3 · answered Jun 06 '13 at 19:28

1

You cannot override method toString on array but you can use Arrays.toString(Object[]) to print array.

answered Jun 06 '13 at 19:28

Grzegorz Żur

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score 1 · Answer 4 · answered Jun 06 '13 at 19:34

1

First of all, you don't need to extend Object, it is there by default.

To print the array content you can use:

Person[] persons = new Person[3];
System.out.println(Arrays.toString(persons));

answered Jun 06 '13 at 19:34

Ederson

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Java overloading toString() method when array of class is given

4 Answers4

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