Does java have an equivalent to python __call__?

Question

Just started learning python, I've come across __call__ method. I understand when __init__ gets called and when __call__ gets called by running a simple example:

class Constructor:
    def __init__(self, a):
        print "__init__ called"

    def __call__(self):
        print "__call__ called"

    def dummy(self):
        print "a dummy method called"

print "creating x obj"
x = Constructor(1)
print "calling x object"
x()

console output:

creating x obj
__init__ called
calling x object
__call__ called

My questions are:

1. I come from java background, I know __init__ maps to java constructor, does java have an equivalent to __call__ to help me understand this better?
2. Can someone give me a simple example of when __call__ can be useful?

Answer 1

__call__ equates to overloading the () operator on a class. This is possible in C++ but not Java. It allows one to have function objects (sometimes called functors).

In Python these are termed callable objects.

In simple terms, this allows you to treat an object as a function.

The actual use for such concepts is beyond the scope of this answer but there is plenty of information around the internet. For example Wikipedia.

Answer 2

Nope, there is nothing like __call__ in Java. You cannot use an object as a method call. You have to create a method and call it:

class Constructor{
    Constructor(){
        System.out.println("Constructor called");
    }

    void doStuff(){
        System.out.println("do called");
    }

    public static void main(String[] args){
        System.out.println("Creatng x obj");
        x = new Constuctor();
        System.out.println("Calling x obj");
        x.doStuff();
    }
}