Abstract In Java

In Java, abstract means incomplete.

It is used when a class or method is not fully finished and child classes must complete it.

Abstract Class

A class declared with abstract keyword is called an abstract class.

abstract class Animal {
}

• Cannot create object directly
• Mostly used as parent class

Animal a = new Animal(); // ❌ Error

Abstract Method

An abstract method has:

• only declaration
• no body

abstract void sound();

Child class must implement it.

Example

abstract class Animal {
    abstract void sound();
}

class Dog extends Animal {
    void sound() {
        System.out.println("Bark");
    }
}

Here:

• Animal gives only idea
• Dog completes the method

Simple Real-Life Example

Think about a “Vehicle”.

All vehicles move, but:

• Car moves differently
• Bike moves differently

So parent class says:

abstract void move();

Child classes define how they move.