Parent and Child Classes Having Same Data Member in Java

In Java, when both a parent class and a child class declare a data member with the same name, the child’s data member hides the parent’s data member. This concept is known as data hiding (variable hiding) and is different from method overriding.

• Data members are not overridden in Java; they are hidden.
• Access to the data member depends on the reference type, not the object type.
• Both parent and child maintain separate copies of the data member.
• Parents’ data member can be accessed using the super keyword.

Example: Parent and Child with Same Data Member

class Parent {
    int x = 10;
}

class Child extends Parent {
    int x = 20;
}

public class Main {
    public static void main(String[] args) {
        Parent p = new Child();
        Child c = new Child();

        System.out.println(p.x);
        System.out.println(c.x);
    }
}

10
20

Explanation:

• Parent and Child both declare a data member named x.
• p.x accesses the data member of the Parent class because the reference type is Parent.
• c.x accesses the data member of the Child class because the reference type is Child.
• This shows that data member access is resolved at compile time.

Accessing Parent Data Member Using super

class Child extends Parent {
    int x = 20;

    void show() {
        System.out.println(x);        // Child's x
        System.out.println(super.x);  // Parent's x
    }
}

Explanation:

• x refers to the child’s data member.
• super.x explicitly accesses the parent’s data member.

Difference Between Method Overriding and Data Member Hiding

When to Avoid Same Data Members

• When it causes confusion in large codebases
• When readability and maintainability are priorities

Variable access in Java depends on the reference type, whereas method calls depend on the object type.