Inheritance , method signature , method overriding and throws clause

Question

My Parent class is :

import java.io.IOException;
public class Parent {
        int x = 0;
        public int getX() throws IOException{
        if(x         


        

Answer 1

Easy to remember

1. Access modifier can be changed from restricted to less restricted,
   for example from protected to public, but not vise versa
2. throws signature can be changes from parent exception to child exception class, but not vise versa

This code is valid

public class A  {

    protected String foo() throws Exception{
        return "a";
    }

    class B extends A {
        @Override
        public String foo() throws IOException{
            return "b";
        }
    }
}

Overrided foo method has public access, not protected and throws IOException that child of Exception

This code is not valid

public class A  {

    public String foo() throws IOException{
        return "a";
    }

    class B extends A {
        @Override
        protected String foo() throws Exception{
            return "b";
        }
    }
}

Overrided foo method has more restricted access modifier and throws Exception that NOT child of IOException

By the way you can override method from superclass and not throw ecxeptions at all

This code valid

public class A  {

    public String foo() throws IOException{
        return "a";
    }

    class B extends A {
        @Override
        public String foo(){
            return "b";
        }
    }
}