Calling a method of a class without creating object of it

Question

class A{
    String z(){
        System.out.println(\"a\");
        return \"sauarbh\";
    }
}
class B{
    A a;
    A x(){
    return a;   
    }
}
public class runner         


        

Answer 1

Class B method x() is not returning new object of A. Instead you are returning object of Class A with null value.

A a; // value of a is null 
A x() {
    return a;
}

In runner class

A a2=b.x(); // b.x() will return a, which is null. so A a2=null
a2.z();    // Equivalent to null.z() throws NullPointerException 

Make below changes in your Class B code:

class B{
    A a;
    A x(){
    return new A();// return new object of Class A;   
    }
}

or

class B{
    A a= new A(); // Initialize Class A with new object 
    A x(){
    return a;   
    }
}