i'd like to say that there is a case you must
use "this" keyword this case if the parameter or a function  the same
as the attributes of the class like this example

class Student
{
private String name;
private int age;
private String email;
public Student()
{
name="";
age=0;
email="";
}
public Student(String name,int age,String email)
{
this.name=name;
this.age=age;
this.email=email;
}
}