Adding ints to final array list

Question

I have an array list (below). The numbers of the list's equivalent char representation print out a secret message (which can be done through type casting). But before I read that, I need to add 5 to each element in the array list first. But I thought as the array is final that we could not change the string elements? (I did try making the array non-final, but still could not increment each value in the list by 5.) You can see the code I have tried to use below, but it still prints out the original values in the list. Does anyone have any pointers? thanks.

public static void main(String[] args) {
    final int[] message = { 82, 96, 103, 103, 27, 95, 106, 105, 96, 28 };
    final int key = 5;
    for (int x : message)
        x = x + key;
    for (int x : message)
        System.out.print(x + ",");
}

rainkinz · Accepted Answer · 2014-02-28 04:46:41Z

3

you are not changing the message array. you are just getting a temp value x for each element then increasing it. even if you tried it would show error as it is declared as final .

to increase the values you can do something like this

int[] message =
    {82, 96, 103, 103, 27, 95, 106, 105, 96, 28};
final int key = 5;
for (int i = 0; i< message.length; i++)
    message[i]+=key;

edited Feb 28, 2014 at 4:46

rainkinz

10.5k5 gold badges49 silver badges74 bronze badges

answered Feb 28, 2014 at 4:44

stinepike

54.9k14 gold badges95 silver badges115 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

evanchooly · Accepted Answer · 2014-02-28 04:44:45Z

0

you don't need that second loop:

for (int x: message) { x = x + key; System.out.print(x + ","); }

In the first loop, you're change a variable (x) local to that loop. You're not actually modifiying the array contents like you seem to be expecting. In the second loop, that x variable is local to the second loop and completely distinct from the x of the first loop.

answered Feb 28, 2014 at 4:44

evanchooly

6,2761 gold badge18 silver badges24 bronze badges

Comments

Drogba · Accepted Answer · 2014-02-28 04:47:06Z

0

Try this

final int[] message = { 82, 96, 103, 103, 27, 95, 106, 105, 96, 28 };
final int key = 5;
for (int i = 0; i < message.length; i++)
  message[i] += key;
for (int i = 0; i < message.length; i++)
  System.out.print(message[i] + ",");

Your code doesn't work because your x is a local variable in the for loop.

answered Feb 28, 2014 at 4:47

Drogba

4,3664 gold badges27 silver badges32 bronze badges

Comments

Yahya Arshad · Accepted Answer · 2014-02-28 04:47:43Z

0

You are adding key in copy of element of array, which will not change value of actual element of array. instead do this.

   for (int x =0; x < message.length; x++)
        message[x] = message[x] + key;
    for (int x : message)
        System.out.print(x + ",");

More clarification

int value = message[0];
value = value+10; // This will not change value of element at message[0];

answered Feb 28, 2014 at 4:47

Yahya Arshad

1,6282 gold badges19 silver badges34 bronze badges

Comments

TheLostMind · Accepted Answer · 2014-02-28 04:48:45Z

0

But I thought as the array is final that we could not change the string elements? I did try making the array non-final

You are getting confused between final and immutable :

final--> 1. For primitives : you can't change the value (RHS)
         2. For non-primitives : you can't reassign the reference to another object.
         2.b. You can change the value(s) of the object to which the reference is currently pointing.

immutable - you can't change the value of the object to which the reference is pointing.

answered Feb 28, 2014 at 4:48

TheLostMind

36.3k12 gold badges72 silver badges109 bronze badges

Collectives™ on Stack Overflow

Adding ints to final array list

5 Answers 5

Comments

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related