What does the syntax mean in Java: new Stream(){ … }?

Question

I have encountered the following Java syntax that I don\'t recognize.

This part is fine:

public abstract class Stream implements Iterator

        

Answer 1

ones = new Stream<Integer>() {
public Integer next() {
return 1; }
};

Assigns a new instance of an anonymous implementation of Stream<Integer> (that contains a virtually unlimited number of 1s. You may find more on anonymous classes in Java In A Nutshell

Answer 2

This is providing an inline (anonymous) subclass of the Stream class.

Functionally, it is the same as:

public NewClass extends Stream {
    public Integer next() {  
       return 1; 
    }  
}

and

void someMethodInAnotherClass {
    Stream stream = new NewClass();
}

but as this class definition isn't used outside the method body, you can define it as anonymous.

Answer 3

This is defining a Anonymous class which implements the Stream interface. To implement the interface we need to implement the method next.