get multiple random values from ArrayList HashMap

Question

I want to get some specific number random values from ArrayList

final ArrayList<HashMap<String, String>> menuItems = new ArrayList<HashMap<String, String>>();

for (int i = 0; i == 4; i++) {

        index = random.nextInt(menuItems.size());
        HashMap<String, String> getitem = menuItems.get(index);
        System.out.println(getitem.get(KEY_NAME));
    }

Nothing is printing out.

Code in loop works if i use it outside loop, but since i need multiple values, i use loop and it doesnt work.

Thought about using a debugger or old style 'printf debugging'? — MrSmith42
– MrSmith42, Commented Feb 16, 2013 at 19:15
Style note but it's a good idea to code to interfaces where possible: final List<Map<String, String>> menuItems = new ArrayList<Map<String, String>>(); — Eric P.
– Eric P., Commented Feb 16, 2013 at 19:19

jlordo · Accepted Answer · 2013-02-27 15:25:03Z

5

change

for (int i = 0; i == 4; i++) { // start with i beeing 0, execute while i is 4
                               // never true

to

for (int i = 0; i < 4; i++) {  // start with i beeing 0, execute while i is
                               // smaller than 4, true 4 times

Explanation:

A for loop has the following structure:

for (initialization; condition; update)

initialization is executed once before the loop starts. condition is checked before each iteration of the loop and update is executed after every iteration.

Your initialization was int i = 0; (executed once). Your condition was i == 4, which is false, because i is 0. So the condition is false, and the loop is skipped.

edited Feb 27, 2013 at 15:25

answered Feb 16, 2013 at 19:12

jlordo

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Comments

assylias · Accepted Answer · 2013-02-16 19:12:40Z

2

The ending condition of your for loop is broken: for (int i = 0; i == 4; i++) should be for (int i = 0; i < 4; i++) (4 iterations) or for (int i = 0; i <= 4; i++) (5 iterations).

This tutorial explains how the for statement works.

answered Feb 16, 2013 at 19:12

assylias

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