Why defult constructor add by compiler ?

Why defult constructor add by compiler ?

Why constructor ?
constructor is ment for initialize instance fields and when you call it through new operator/keyword then only it will create object for corresponding class which u assig as datatype
Ex:-
= = = =
class Test {
Main (String [ ] args ) {
method1();//C.E
}

See in Test class there is no method but I am trying to call method1() from where jvm search this method1() if class doesn't contain method which u call at runtime then it leads compile time error

Similarly
Test {
Main(String [ ] args ) {
Test t = new Test ( )
}
See here Test () is constructor which u call through new keyword for creating object. But constructor is called by whome jvm. Constructor is also an method but the difference between method and constructor is only that constructor doesn't returns any thing.
So if ur class contain doesn't contain constructor then jvm called whome?
That's why compiler restrict to us hey either u place constructor other wise I will place it as defult constructor otherwise I can't get ur class constructor how could I call that's why compiler add defult constructor. ...

new Test();
If compiler doesn't add defult constructor then how could u call Test() it also act like as method (call back method ). .
}