what's the point of java constructor?

Question

So I\'m learning java. I\'m one month in and I just learned about constructors. But I don\'t see the whole purpose of creating one. Why and when would I ever want to use one

Answer 1

Actually constructor is needed IF you need to assign unique initial state to an instance of a class. In Java i only just realized (by a friend) that we can do this:

public class MyClass1 {
     private class MyClass2 {}
     private MyClass2 myobj2 = new MyClass2();
}

So no need for implicit constructor. But if something like follows, you need constructor.

public class MyClass1 {
     private class MyClass2 { 
         private int id_ = 0;
         public MyClass2(int id) { id_ = id; }    // how to reach this?   
     }

     private MyClass2 myobj2 = new MyClass2(1);   // (this doesn't work. Not unique)

     public MyClass1(int id)     { myobj2 = new MyClass2(id); }   // by this!
}
MyClass1 obj1 = new MyClass1(100);
MyClass1 obj2 = new MyClass1(200);