Java Utililty Methods Collection First

List of utility methods to do Collection First

  1. HOME
  2. Java
  3. C
  4. Collection First

Description

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

Method

TgetFirst(Collection set, boolean remove)
get First 
Iterator<T> iterator = set.iterator();
if (!iterator.hasNext()) {
    throw new IllegalStateException("The set is empty");
T first = iterator.next();
if (remove) {
    iterator.remove();
return first;
TgetFirst(Collection ts)
get First 
final Iterator<T> it = ts.iterator();
return it.hasNext() ? it.next() : null;
TgetFirst(final Collection collection)
get First 
return collection == null ? null : collection.iterator().next();
TgetFirstAndOnly(Collection c)
get First And Only 
if (c.size() != 1) {
    throw new Error("Size must be 1 but was " + c.size());
return getFirst(c);
UgetFirstClassOfType(Collection l, Class type)
Get the first class of type U in the collection 
for (T o : l) {
    if (type.isInstance(o)) {
        return type.cast(o);
return null;
TgetFirstElement(Collection coll)
INTERNAL: Gets the first object in the collection. 
if (coll instanceof List)
    try {
        return ((List<T>) coll).get(0);
    } catch (IndexOutOfBoundsException e) {
        throw new NoSuchElementException();
else
    return coll.iterator().next();
...
TgetFirstElement(Collection collection, T defaultValue)
get First Element 
T elem = defaultValue;
if (collection != null && !collection.isEmpty()) {
    if (List.class.isAssignableFrom(collection.getClass())) {
        elem = ((List<T>) collection).get(0);
    } else {
        for (T item : collection) {
            elem = item;
            break;
...
EgetFirstElementOrNull(Collection collection)
returns the first element of a collection or null if the collection is empty. 
if (collection.isEmpty()) {
    return null;
} else {
    return collection.iterator().next();
TgetFirstElementOrNull(Collection coll)
get First Element Or Null 
if (coll == null || coll.isEmpty())
    return null;
return coll.iterator().next();
ObjectgetFirstItem(Collection c)
Return the first item from a collection using the most efficient method possible. 
if (c instanceof List) {
    return ((List) c).get(0);
return c.iterator().next();