What are the key differences between interfaces and abstract classes in Java?

Interface Definition in Java

An interface in Java provides a mechanism to define a contract between classes, specifying methods that must be implemented without providing their implementations. It's like a blueprint that defines the shape and structure of a building without specifying the materials.

Syntax

interface InterfaceName {
    public abstract void method1();
    public abstract void method2();
}

Java assumes all methods within an interface are implicitly declared as public abstract. Therefore, you can省略 the public abstract keywords in your code.

Implementation

To implement an interface, a class must implement all of its methods:

public class ImplementingClass implements InterfaceName {
    public void method1() { /* implementation */ }
    public void method2() { /* implementation */ }
}

Multiple Implementations

Multiple classes can implement the same interface. This provides flexibility in defining contracts for different use cases.

Multiple Interfaces

A class can implement multiple interfaces, allowing it to adhere to different contracts simultaneously.

Difference from Abstract Classes

Interfaces and abstract classes share similarities but differ in two key aspects:

1. Method Implementation: Interfaces cannot have method implementations, while abstract classes can.
2. Multiple Inheritance: Classes can implement multiple interfaces but can only inherit from one abstract class.

Benefits of Interfaces

• Enforce contracts for classes to follow.
• Promote loose coupling between classes.
• Facilitate code reuse and extensibility.
• Allow for polymorphism, where objects with different implementations can be treated as having a common type.

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