Code explanation with strings

Question

Okay, so I am trying to be able to explain the answer to the question below to a friend, but I don't know how. I know that the process method doesn't change s and that the answer is ABCD (s is unchanged), but I don't know why. Is it because strings are immutable? My friend thinks it should be CBA. Any help?

public void process(String s) 
{
    s = s.substring(2, 3) + s.substring(1, 2) + s.substring(0, 1);
}

What is printed as a result of executing the following statements (in a method in the same class)?

String s = “ABCD”;
process(s);
System.out.println(s);

Just try it, don't ask questions like this please it has no use to others — Squareoot, Dec 20 '17 at 19:24
Your reassignment of string s is local to the function process only. Java passes parameters by value, so the callers reference is unchanged. — StuartLC, Dec 20 '17 at 19:25

score 0 · Answer 1 · answered Dec 20 '17 at 19:27

0

You are assigning a new value to the variable s. This does not change the value of s which is passed to the process() method, so the program prints

ABCD

answered Dec 20 '17 at 19:27

cdbbnny

330
2
9

score 0 · Answer 2 · answered Dec 20 '17 at 19:27

that happens, because you are calling it by it's value, and it doesn't change

you can rewrite your method such as :

public static String process(String s) 
{
    return s.substring(2, 3) + s.substring(1, 2) + s.substring(0, 1);
}

and then you can use it like this :

String s = "ABCD";
s = process(s);
System.out.println(s);

Code explanation with strings

2 Answers2