What does (angle brackets) mean in Java?

Question

I am currently studying Java and have recently been stumped by angle brackets(<>). What exactly do they mean?

public class Pool{
    public inter         


        

Answer 1

It's really simple. It's a new feature introduced in J2SE 5. Specifying angular brackets after the class name means you are creating a temporary data type which can hold any type of data.

Example:

class A{
    T obj;
    void add(T obj){
        this.obj=obj;
    }
    T get(){
        return obj;
    }
}
public class generics {
    static void print(E[] elements){
        for(E element:elements){
            System.out.println(element);
        }
    }

    public static void main(String[] args) {
        A obj=new A();
        A obj1=new A();
        obj.add("hello");
        obj1.add(6);
        System.out.println(obj.get());
        System.out.println(obj1.get());

        Integer[] arr={1,3,5,7};
        print(arr);
    }
}

Instead of , you can actually write anything and it will work the same way. Try writing in place of .

This is just for convenience:

• is referred to as any type
• as element type
• as number type
• as value
• as key

But you can name it anything you want, it doesn't really matter.

Moreover, Integer, String, Boolean etc are wrapper classes of Java which help in checking of types during compilation. For example, in the above code, obj is of type String, so you can't add any other type to it (try obj.add(1), it will cast an error). Similarly, obj1 is of the Integer type, you can't add any other type to it (try obj1.add("hello"), error will be there).