How to get the random values from List in java>

Question

Here my code is,

List<HashMap<ArrayList<String>, ArrayList<ArrayList<String>>>> al = new ArrayList<HashMap<ArrayList<String>, ArrayList<ArrayList<String>>>>();

from above list i am getting values like below:

for (HashMap<ArrayList<String>, ArrayList<ArrayList<String>>> entry : al) {

            for (Entry<ArrayList<String>, ArrayList<ArrayList<String>>> mapEntry : entry
                    .entrySet()) {
                key = mapEntry.getKey();
                value = mapEntry.getValue();
            }

        }

I am getting values without any problem,Here my problem is i need to get values randomly(not duplicate values).How i can get the values randomly.Please can any one help me.

Thanking in Advance.

http://stackoverflow.com/questions/929554/is-there-a-way-to-get-the-value-of-a-hashmap-randomly-in-java/929769#929769 — Suresh Atta, Oct 24 '13 at 09:40
Do you want random values from `HashMap`, or you also want those `HashMap`s to be chosen at random? — Rohit Jain, Oct 24 '13 at 09:45

score 4 · Answer 1 · answered Oct 24 '13 at 09:43

4

Shuffle the list then iterate over it.

answered Oct 24 '13 at 09:43

amal

1,369
8
15

score 1 · Answer 2 · answered Oct 24 '13 at 09:51

1

Try this out:

HashMap<String, Integer> map = new HashMap<String, Integer>();
map.put("abc", 1);
map.put("def", 2);
map.put("ghi", 3);

//Creating a list
List<Integer> list = new ArrayList<Integer>(map.values());

//Generating a random value
int index = new Random().nextInt(list.size());

//Result
Integer value = list.get(index);

answered Oct 24 '13 at 09:51

Siddh

712
4
21

It is worked but duplicates are repeated – user2681425 Oct 24 '13 at 12:07
@user2681425 try this link with no repeats http://stackoverflow.com/questions/15258063/java-random-values-that-not-repeat – Siddh Oct 24 '13 at 13:30
@user2681425 it will help to you – Siddh Oct 24 '13 at 13:32

Mickey Tin · Answer 3 · 2014-07-08T08:33:55.513

1

Simple util generic method :

static public <T> T getRandom(List<T> list){
    if(list == null || list.isEmpty()){
        return null;
    }else{
        return list.get(rand.nextInt(list.size()));
    }
}

edited Jul 08 '14 at 08:33

answered Jul 08 '14 at 00:00

Mickey Tin

3,408
10
42
71

1

Answers that just contain code blocks aren't always as self explanatory as they may seem to the people who wrote them. Can you explain how your code answers the question? – apaul Jul 08 '14 at 00:23

score 0 · Answer 4 · answered Oct 24 '13 at 09:49

0

Use shuffle() in collections class.It will satisfy your need.

List list=new ArrayList(); Collections.shuffle(list);

answered Oct 24 '13 at 09:49

Navin

21
2

List, ArrayList>>> al = new ArrayList, ArrayList>>>(); Collections.shuffle(al); – user2681425 Oct 24 '13 at 09:52
but i am not getting random values – user2681425 Oct 24 '13 at 09:54

score 0 · Answer 5 · answered Sep 03 '15 at 05:08

0

You can use ThreadLocalRandom. Check http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ThreadLocalRandom.html for further details.

Similar to what Siddh has suggested.

answered Sep 03 '15 at 05:08

richa_v

119
1
7

How to get the random values from List in java>

5 Answers5