What are Interfaces in Java and how do they differ from Abstract Classes?

Understanding Interfaces in Java

An interface in Java is a unique type of abstract class that defines methods without providing implementations. It enforces a contract between classes that implement it, specifying the methods they must have, but not their behavior.

Creating an Interface:

interface InterfaceName
{
    void interfaceMethodName();
}

Implementing Interfaces:

Classes can implement multiple interfaces. Each implemented interface's methods must be defined in the class.

public class ImplementingClass implements InterfaceA, InterfaceB
{
    public void interfaceMethodA() { /* Implementation */ }
    public void interfaceMethodB() { /* Implementation */ }
}

Key Differences from Abstract Classes:

1. Method Implementation: Interfaces cannot implement methods, while abstract classes can.
2. Multiple Inheritance: Classes can extend only one abstract class but can implement multiple interfaces.

Advantages and Limitations of Multiple Interfaces:

Multiple interfaces allow for flexibility and code reuse by defining reusable functionality as separate contracts. However, if two interfaces declare conflicting method signatures, it can lead to runtime errors.

مثال on Using Interfaces:

interface InterfaceA
{
    void methodA();
}

interface InterfaceB
{
    void methodB();
}

public class ImplementingClass implements InterfaceA, InterfaceB
{
    public void methodA() { System.out.println("InterfaceA, MethodA"); }
    public void methodB() { System.out.println("InterfaceB, MethodB"); }
}

In this example, the ImplementingClass must implement both methodA and methodB as per the contracts defined by InterfaceA and InterfaceB respectively.

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