Java Utililty Methods Collection Unique

List of utility methods to do Collection Unique

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Description

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

Method

booleanhasUniqueObject(Collection collection)
CollectionUtils Determine whether the given Collection only contains a single unique object. 
if (collection == null || collection.isEmpty()) {
    return false;
boolean hasCandidate = false;
Object candidate = null;
for (Object elem : collection) {
    if (!hasCandidate) {
        hasCandidate = true;
...
Collectionunique(Collection c)
unique 
if (c != null && c.size() > 0) {
    Map<T, Integer> map = new LinkedHashMap<T, Integer>();
    for (T o : c) {
        map.put(o, 0);
    return new ArrayList<T>(map.keySet());
return c;
...
Collectionunique(Collection c, Collection result)
unique 
if (c == null) {
    return result;
Set<T> s = new LinkedHashSet<T>(c);
result.addAll(s);
return result;
StringuniqueIdNotIn(String prefix, Collection exclusions)
unique Id Not In 
StringBuilder sb = new StringBuilder(prefix);
for (int counter = 0;; ++counter) {
    sb.setLength(prefix.length());
    sb.append('.').append(counter);
    String candidate = sb.toString();
    if (!exclusions.contains(candidate)) {
        return candidate;
TuniqueResult(Collection results)
Method to take a get a unique result from a set and return it or null. 
return results.isEmpty() ? null : results.iterator().next();
TuniqueResult(final Collection c)
unique Result 
switch (c.size()) {
case 0:
    return null;
case 1:
    return c.iterator().next();
default:
    throw new IllegalStateException("Unexpected number of elements in collection: " + c.size());