CODEWITHSUNDEEP
javatostring
endless
endless

Reputation: 3453

Any reason to use toString() method explicitly to print an object in Java

Just wondering if there is ever any reason to call toString() explicitly on an object to print it?

MyClass obj = new MyClass(); // Assume toString() method is overriden in this class
System.out.println(obj);

System.out.println(obj.toString());

I obviously use the first approach, but one of my co-workers argues that I should put back that obj.toString()! I feel toString() is just redundant and not using it actually reduces the chances of NPE!

Am I missing something or do people have any reason to use toString() explicitly?

Upvotes: 3

Views: 1690

Answers (3)

Sean Owen
Sean Owen

Reputation: 66886

System.out is an instance of PrintStream. If you call println() you will be calling this code:

public void println(Object x) {
    String s = String.valueOf(x);
    synchronized (this) {
        print(s);
        newLine();
    }
}

So it's just converting to a String anyway, although using String.valueOf. The difference is that String.valueOf(null) is "null" and just calls toString() on the object anyway if it's not null. But calling toString() on null causes a NullPointerException for sure.

So, use the former. It's simpler and handles null.

Upvotes: 8

elbuild
elbuild

Reputation: 4899

If obj is null the second call will generate an NPE as you pointed out. As @Louis said, provided obj is not null, they're basically the same thing.

I would prefere to override toString() if I want to customize the literal rapresentation of MyClass, calling it WITHOUT the .toString() method to avoid the risk of NPE.

Upvotes: 4

venergiac
venergiac

Reputation: 7717

IMHO do not use toString() explicitly, it could cause null pointer exception

Upvotes: 4

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