What are some examples of type constraints in Java?

What are some examples of type constraints in Java?

In Java, type constraints can be applied using generics. For example, you can use the extends keyword to restrict a type parameter to a specific class or interface.

Can you give me a specific code example?

Sure! Here's a simple example:

class Box<T extends Number> {
    private T item;
    public void setItem(T item) { this.item = item; }
    public T getItem() { return item; }
}

In this case, T can only be a subclass of Number.

What happens if I try to use a non-Number type?

If you try to use a non-Number type, like String, the compiler will throw an error, ensuring type safety.

Are there other ways to apply type constraints?

Yes, you can also use multiple bounds with the & operator, or use wildcards with ? extends and ? super for more flexibility.