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Abstract Classes

Abstract classes can have abstract and concrete methods. They cannot be instantiated.

Code Examples

Abstract class with concrete and abstract methods

java

1
2abstract class Animal {
3    abstract void sound();
4
5    void eat() {
6        System.out.println("Eating");
7    }
8}
9
10class Dog extends Animal {
11    void sound() {
12        System.out.println("Dog barks");
13    }
14}
15

Use Cases

Base class with shared code
Template method pattern

Common Mistakes to Avoid

Trying to instantiate abstract class
Forgetting to implement abstract methods