Thread: this in Java for particular example

Hi All,

I've read some information for this but would like if you explain me why the output is different for this particular example.

package test03aug;
 
public class MainClass {
	public static void main(String[] a) {
		Exam e=new Exam();
		System.out.println(e.age);
		e.modifyVal(e.age);
		System.out.println(e.age);
	}
 
}
 
class Exam {
int age;
void modifyVal(int age){
age=age+1;
	System.out.println(age);
}
}

output:
0
1
0

package test03aug;
 
public class MainClass {
	public static void main(String[] a) {
		Exam e=new Exam();
		System.out.println(e.age);
		e.modifyVal(e.age);
		System.out.println(e.age);
	}
 
}
 
class Exam {
int age;
void modifyVal(int age){
this.age=age+1;
	System.out.println(age);
}
}

0
0
1

Welcome to the forum! Thanks for taking the time to learn how to post code correctly. If you haven't already, please read this topic to learn other useful info for new members.

Why do you think? Trace the code, paying particular attention to the println() statements and the values of the variables being printed by them. If you want confirmation or correction, post what you're thinking and ask us for input.

The this keyword in Java refers to the object executing the code, in this case the Exam object you create. In this context, using this modifies the globally scoped age field in the object, without this you refer to the locally scoped age variable in the modifyVal method.