java - how do you know what parameters go inside the parentheses when creating a new object? -

i in process of learning java programming. see code looks this:

shape ball= new shape();.// takes no parameter shape ball= new shape(1,2); //takes parameter 

my question is, when object has multiple constructors take different paramaters, how know constructor use?

look @ documentation class. that's surefire way know. shape class provided has 2 constructors:

shape() //default no-args {     //do }  shape(int a, int b) {     //do , b }