Generics

Generics in Java provide a way to create classes, interfaces, and methods that operate on any data type while still providing type safety at compile time. Generics allow you to write reusable code that can work with different data types without the need for explicit type casting. Let's explore generics in more detail:

1. Introduction to Generics

Generics were introduced in Java 5 to address the need for type-safe collections and to make Java programs more robust and easier to read. They allow you to create classes, interfaces, and methods that can work with any data type.

2. Generic Classes

You can create generic classes by specifying one or more type parameters in angle brackets (`<>`). These type parameters represent placeholder types that are replaced with actual types when an object of the generic class is created.

public class Box<T> {

    private T value;

    public void setValue(T value) {
        this.value = value;
    }

    public T getValue() {
        return value;
    }
}

3. Using Generic Classes

When creating objects of a generic class, you specify the actual type for the type parameter.

Box<Integer> intBox = new Box<>();
intBox.setValue(10);
int value = intBox.getValue(); // No need for explicit type casting

4. Generic Methods

You can also create generic methods that can operate on any data type. Type parameters for generic methods are declared before the return type.

public <T> T getLastElement(T[] array) {
    if (array.length == 0) {
        return null;
    }
    return array[array.length - 1];
}

5. Using Generic Methods

String[] names = {"Alice", "Bob", "Charlie"};
String lastElement = getLastElement(names);

Integer[] numbers = {1, 2, 3};
Integer lastNumber = getLastElement(numbers);

6. Generic Interfaces

You can define generic interfaces similar to generic classes, using type parameters.

public interface List<T> {
    void add(T element);
    T get(int index);
}

7. Bounded Type Parameters

You can restrict the types that can be used as type parameters using bounded type parameters.

public <T extends Number> void printNumber(T number) {
    System.out.println(number);
}

Conclusion

Generics in Java provide a powerful way to write reusable and type-safe code. They allow you to create classes, interfaces, and methods that can work with any data type while still providing type safety at compile time. Understanding how to use generics effectively is essential for writing flexible and maintainable Java code.