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.

Do you want random values from HashMap, or you also want those HashMaps to be chosen at random? — Rohit Jain
– Rohit Jain, Commented Oct 24, 2013 at 9:45

amal · Accepted Answer · 2013-10-24 09:43:17Z

4

Shuffle the list then iterate over it.

answered Oct 24, 2013 at 9:43

amal

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Comments

Siddh · Accepted Answer · 2013-10-24 09:51:23Z

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, 2013 at 9:51

Siddh

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3 Comments

user2681425 Over a year ago

It is worked but duplicates are repeated

Siddh Over a year ago

@user2681425 try this link with no repeats stackoverflow.com/questions/15258063/…

Siddh Over a year ago

@user2681425 it will help to you

Mickey Tin · Accepted Answer · 2014-07-08 08:33:55Z

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 8, 2014 at 8:33

answered Jul 8, 2014 at 0:00

Mickey Tin

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1 Comment

apaul Over a year ago

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?

Navin · Accepted Answer · 2013-10-24 09:49:58Z

0

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

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

answered Oct 24, 2013 at 9:49

Navin

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2 Comments

user2681425 Over a year ago

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

user2681425 Over a year ago

but i am not getting random values

richa_v · Accepted Answer · 2015-09-03 05:08:05Z

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 3, 2015 at 5:08

richa_v

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