Method overriding rules in Java - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to override the method display in the subclass.

Java

class Parent {
    void display() {
        System.out.println("Parent display");
    }
}

class Child extends Parent {
    @Override
    public void [1]() {
        System.out.println("Child display");
    }
}

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Ashow

Bprint

Cdisplay

DdisplayMessage

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different method name in the subclass.

Forgetting the @Override annotation (not mandatory but recommended).

The method name in the subclass must exactly match the method name in the parent class to override it. Here, display is the correct method name.

2fill in blank

medium

Complete the code to override the method with the correct return type.

Java

class Parent {
    int getNumber() {
        return 10;
    }
}

class Child extends Parent {
    @Override
    public [1] getNumber() {
        return 20;
    }
}

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Aint

Bvoid

CString

Ddouble

Attempts:

3 left

💡 Hint

Common Mistakes

Changing the return type to a different incompatible type.

Using void when the parent method returns a value.

The return type in the overriding method must be the same or a subtype (covariant) of the parent method's return type. Here, int matches exactly.

3fill in blank

hard

Fix the error in the method overriding by choosing the correct access modifier.

Java

class Parent {
    protected void show() {
        System.out.println("Parent show");
    }
}

class Child extends Parent {
    @Override
    [1] void show() {
        System.out.println("Child show");
    }
}

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Afinal

Bdefault

Cprivate

Dprotected

Attempts:

3 left

💡 Hint

Common Mistakes

Using private in the child method which is more restrictive.

Using final which prevents overriding.

The overriding method cannot have a more restrictive access modifier. Since the parent method is protected, the child method must be protected or more accessible.

4fill in blank

hard

Fill both blanks to correctly override the method and handle exceptions.

Java

class Parent {
    void process() throws [1] {
        System.out.println("Parent process");
    }
}

class Child extends Parent {
    @Override
    void process() throws [2] {
        System.out.println("Child process");
    }
}

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AIOException

BException

CFileNotFoundException

DRuntimeException

Attempts:

3 left

💡 Hint

Common Mistakes

Throwing a broader exception in the child method.

Throwing an unrelated exception.

The child method can only throw the same or narrower exceptions. FileNotFoundException is a subclass of IOException, so this is allowed.

5fill in blank

hard

Fill all three blanks to correctly override the method with covariant return type and access modifier.

Java

class Parent {
    Number getValue() {
        return 10;
    }
}

class Child extends Parent {
    @Override
    public [1] getValue() {
        return new [2]();
    }
}

class [3] extends Number {
    public int intValue() { return 0; }
    public long longValue() { return 0L; }
    public float floatValue() { return 0.0f; }
    public double doubleValue() { return 0.0; }
}

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ANumber

BInteger

CMyNumber

Dprotected

Attempts:

3 left

💡 Hint

Common Mistakes

Using a return type not related to Number.

Using a more restrictive access modifier than the parent method.

The overriding method must have the same or more accessible modifier (here public is already set), the return type can be a subclass of the parent's return type (covariant). MyNumber extends Number and is returned.