Question

Java Method Resolution :

Consider the following example: What is printed on the console if Main is executed, and why? How the codes could be improved?

public class Main {
    public static void main(String[] args) throws Exception {
        A obj = null;
        obj.foo();
    }
}

public class A {
    public void foo() {
        System.out.println(“foo in A”);
    }
}

Answer 1

// Screenshot of the code & output

Explanation:

The Null Pointer Exception error raised due Class A instance variable reference is set to null and we can't call instance method on reference variable.

When we are creating an object or instance of a class by using new() and then compiler allocates memory dynamically for it's properties and address of memory location is assign to reference variable obj.

Working code
// Screenshot of the code & output

// code to copy

A.java

public class A {
   public void foo() {
System.out.println("foo in A");
}
}

Main.java

public class Main {

   public static void main(String[] args) {
       A obj = new A();
   obj.foo();
   }

}