How has variance and invariance changed in recent Java versions?

In recent Java versions, notably from Java 7 onwards, variance and invariance concepts have continued to play a crucial role in type safety and generics. Variance refers to how subtyping between more complex types relates to subtyping between their components, while invariance means that generic types are not interchangeable even if their component types are related. Understanding these concepts is important for writing flexible and safe code.

The introduction of features like the diamond operator in Java 7 and enhancements in Java 8 (such as lambda expressions) have made it easier to work with generics. Also, wildcards (`? extends T` and `? super T`) allow for more flexibility in method parameters, enabling better handling of variance in collections.

For example, you can use wildcards to allow for a method that accepts a more flexible range of input types:

class Box<T> {
    private T item;

    public void setItem(T item) {
        this.item = item;
    }

    public T getItem() {
        return item;
    }
}

public static void addToBox(Box<? super Integer> box) {
    box.setItem(10); // Works fine
}