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Reputation: 2220

Can we call methods of non-static classes without an object in Java?

The wrapper class Integer has the static method parseInt() which is used like this:

Integer.parseInt();

I thought only methods of static classes could be called like this (i.e. Class.doMethod()). All non-static classes need objects to be instantiated to use their methods.

I checked the API, and apparently Integer is declared as public final Integer - not static.

Upvotes: 0

Views: 2252

Answers (4)

pb2q
pb2q

Reputation: 59607

Any class can contain both static and non-static methods. When calling the static methods on any class - including your own - you don't need to instantiate an instance of the class, just call the method using the class name: MyClass.methodName().

In fact, even the following will work:

Integer nullInt = null;
nullInt.parseInt("5");

This works because only the class type of the reference is important when calling static methods. But consider this poor style: always use e.g. Integer.parseInt instead.

Also note that you can't declare a top-level class as static anyway: only nested/inner classes can be declared as static.

Upvotes: 7

Makoto
Makoto

Reputation: 106390

A way to phrase it: An Integer is a concrete object; you can have many Integers. There is only one Integer.MAX_VALUE.

That's to say, there are some things with Integers that are concrete, and others that only need to exist once, anywhere.

Upvotes: 0

Anthony
Anthony

Reputation: 686

In java, static methods may be called from objects, but this only generates a warning and still compiles. A non-static class can have static fields and methods that are shared by all instances (this is why "Shared" means static in VB.NET). Therefore accessing a static member from an object can confuse the reader, and must be avoided.

Upvotes: 2

Cristopher
Cristopher

Reputation: 323

No, you are wrong.

Only static methods can be called like this, but they may belong to 'non static' classes.

Upvotes: 2

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