How am I able to call a method on a null object?

Question

public class JavaPuzzler {

    public static void main(String[] args) {
    JavaPuzzler javaPuzzler = null;
    System.out.println(javaPuzzler.get());
    }

    private static String get(){
        return "i am a java puzzler";
    }
}

You might think that it should throw NullPointerException because the main method invokes get() method on local variable which is initialized to null, and you can’t invoke a method on null.

But if you run this program, you will see that it prints “i am a java puzzler”.

Can anybody give me the answer. Thanks in advance.

Answer 1

In your code sample, get() is a static member that belongs to the class, not to an instance. You do not need an instance in order to invoke the method.

public static String get() // belongs globally to class, no instance required
public String get() // belongs to instance

Answer 2

It's because the method is static and though you reference an instance, the instance isn't necessary. The Java Language Specification explains why in section 8.4.3.2:

A method that is declared static is called a class method. A class method is always invoked without reference to a particular object.

This means that it does not matter if javaPuzzler instance is null - the method "belongs" to the class, not an instance.

Answer 3

The get method is static, which means that the actual reference in javaPuzzler is ignored in that call, only the variable's type is used.