What is the diamond problem in multiple inheritance, and how does Java handle it?

The Diamond Problem: It occurs in multiple inheritance when a class inherits from two classes that have a common base class. This can create ambiguity about which inherited method to execute.

Example (in other languages):

class A {
    void display() {
        System.out.println("Class A");
    }
}

class B extends A {}
class C extends A {}

class D extends B, C { // Ambiguity: which 'display()' method to call? }

How Java Handles It: Java avoids the diamond problem by not supporting multiple inheritance with classes. Instead, Java uses interfaces to achieve multiple inheritance. If a class implements multiple interfaces with default methods having the same name, the ambiguity must be resolved explicitly.

Example:

interface A {
    default void display() {
        System.out.println("Interface A");
    }
}

interface B {
    default void display() {
        System.out.println("Interface B");
    }
}

class C implements A, B {
    @Override
    public void display() {
        // Resolving the conflict explicitly
        A.super.display();
        B.super.display();
    }
}

public class Main {
    public static void main(String[] args) {
        C obj = new C();
        obj.display();
    }
}