What is the diamond operator, and how does it work?

The diamond operator (<>) is a feature introduced in Java 7 that simplifies the use of generics by allowing the compiler to automatically determine the generic type arguments. It eliminates redundant type declarations, making code cleaner, easier to read, and less error-prone.

Key Points:

• Reduces repetitive generic type declarations during object creation. • Improves code readability and maintainability. • The compiler automatically infers the generic type from the reference variable. • Works with generic classes such as List, Map, Set, Queue, and custom generic classes. • Helps prevent mistakes caused by mismatched generic type declarations.

Example:

Without the diamond operator, developers must specify the generic type twice. With the diamond operator, the compiler infers the type automatically, resulting in cleaner code.

Code Example:

import java.util.ArrayList;
import java.util.List;

public class DiamondOperatorDemo {

    public static void main(String[] args) {

        // Before Java 7
        List<String> names1 = new ArrayList<String>();

        // Using Diamond Operator
        List<String> names2 = new ArrayList<>();

        names2.add("Java");
        names2.add("Spring Boot");

        System.out.println(names2);
    }
}

Interview Tip:

A concise interview answer is: "The diamond operator (<>) was introduced in Java 7 to simplify generic type declarations. It allows the compiler to infer generic types automatically, reducing code duplication and improving readability while maintaining type safety."