Question

How to use inheritance in Java

Answer 1

class MyClass {
    public int n_base; 

    // constructor 
    public MyClass(int n_b) { 
        this.n_base = n_b; 
    } 
          
    public void minus(int minus_n) { 
        n_base -= minus_n; 
    } 
          
    public void plus(int plus_n) { 
        n_base += plus_n; 
    } 
      
    public String toString() { 
        return "n_basee = " + n_base + "\n";
    }  
} 
  
class Test extends MyClass { 
    public int n_derived; 

    public Test(int n_b, int n_d)  { 
        super(n_b); 
        n_derived = n_d; 
    }  
          
    public void set_n_derived(int n_d) { 
        n_derived = n_d; 
    }  
      
    // overriding toString() method of MyClass 
    @Override
    public String toString() { 
        return super.toString() + n_derived; 
    } 
}


public class MainClass  
{ 
    public static void main(String args[]) { 
        Test o = new Test(3, 99); 
        
        System.out.println(o.toString());
              
    } 
}



/*
run:

n_basee = 3
99
 
*/

 

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Answer 2

class A {
    public A() {    
        System.out.println("public A()");  
    }
}
class B extends A {}

public class C {
    public static void main(String[] args) {    
        B ob = new B();  
    }
}



/*
run:

public A()

*/

 

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Answer 3

class B {
    public void p(double d) {    
        System.out.println(d * 3);  
    }
}

class A extends B { 
    // overrides the method p in class B
    public void p(double x) {    
        System.out.println(x);   
    }
}
public class Test {
    public static void main(String[] args) {    
        A oa = new A();    
        
        oa.p(3);    
        oa.p(3.14);  
        
    }
    
}


/*
run:

3.0
3.14

*/

 

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