Question

I have this code from Java project helper.

javaProject.setRawClasspath(new IClasspathEntry[0], null);

How new IClasspathEntry[0] works?

1. How an interface is instantiated with new?
2. How an array [0] is used instead of parenthesis () with new?

ADDED

I think it’s a safer way of saying null.

Answer 1

1.How an interface is instantiated with new?

No, an Interface can never be instantiated.

2.How an array [0] is used instead of parenthesis () with new?

IClasspathEntry[0] is just an element of type IClasspathEntry(well, asubtype of IClasspathEntry) at index zero in your array. you can’t instantiate an interface.

IClasspathEntry[] arr = new IClasspathEntry[size];

The above just creates an array of type IClasspathEntry which accepts subtypes(class's which implement IClasspathEntry) elements.

Sample Code :

interface IClasspathEntry {}

class Xyz implements IClasspathEntry {}

class main
{
    public static void main(String...args)
    {
        IClasspathEntry[] arr = new IClasspathEntry[1];
        IClasspathEntry inst = new Xyz();
        arr[0] = inst;
    }
}