Java Utililty Methods Collection Random Element

List of utility methods to do Collection Random Element

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Description

The list of methods to do Collection Random Element are organized into topic(s).

Method

TchooseElement(Collection elements, T alternative)
choose Element 
return chooseElement((T[]) (elements.toArray()), alternative);
ObjectchooseRandomThing(Collection possibleroutes)
Function chooseRandomPath -------------------------- This function takes in a set of possible routes and simply chooses a random element from the list. 
if (possibleroutes == null) {
    return null;
int size = possibleroutes.size();
int item = new Random().nextInt(size);
int i = 0;
for (Object p : possibleroutes) {
    if (i == item)
...
TchooseWithoutCheck(Collection collection, long seed)
choose Without Check 
int index = new Random(seed).nextInt(collection.size());
Optional<? extends T> result = collection.stream().skip(index).findFirst();
assert result.isPresent();
return result.get();
List>generateMetricsDataWithAllWrongTypes(String metricPostfix, boolean generateRandomTenant, long collectionTime)
generate Metrics Data With All Wrong Types 
List<Map<String, Object>> metricsList = new ArrayList<Map<String, Object>>();
Map<String, Object> testMetric = new TreeMap<String, Object>();
if (generateRandomTenant) {
    testMetric.put("tenantId", random.nextInt());
testMetric.put("metricName", "mzord.string.metric" + metricPostfix);
testMetric.put("ttlInSeconds", 1234566);
testMetric.put("unit", "milliseconds");
...
List>generateMetricsDataWithPartialWrongTypes(String metricPostfix, boolean generateRandomTenant, long collectionTime)
generate Metrics Data With Partial Wrong Types 
List<Map<String, Object>> metricsList = generateMetricsDataWithAllWrongTypes(metricPostfix,
        generateRandomTenant, collectionTime);
Map<String, Object> testMetric = new TreeMap<String, Object>();
if (generateRandomTenant) {
    testMetric.put("tenantId", random.nextInt());
testMetric.put("metricName", "mzord.small.numeric.metric" + metricPostfix);
testMetric.put("ttlInSeconds", 1234566);
...
VgetRandom(Collection collection)
get Random 
if (collection.isEmpty()) {
    return null;
int randIdx = (int) Math.round(Math.random() * (collection.size() - 1));
int count = 0;
Iterator<V> iterator = collection.iterator();
while (iterator.hasNext()) {
    V current = iterator.next();
...
SetgetRandomNumber(Collection collection, int number)
Returns at random a specific number of elements from a collection. 
List<T> list = new ArrayList<T>(collection);
Collections.shuffle(list);
return new HashSet<T>(list.subList(0, number));
TnextItem(Collection items, Random random)
next Item 
int randomIndex = random.nextInt(items.size());
int count = 0;
for (T item : items) {
    if (count == randomIndex)
        return item;
    count++;
return null;
...
ToneOf(Collection array)
one Of 
List<T> list = new ArrayList<T>(array);
return list.get(cInt(0, array.size() - 1));
KpeekRandom(Collection collection, Random rnd)
peek Random 
int size = collection.size();
if (size == 0) {
    return null;
int index = rnd.nextInt(size);
List<K> values = new ArrayList<K>(collection);
return values.get(index);