Example usage for java.util Collection iterator

Introduction

In this page you can find the example usage for java.util Collection iterator.

Prototype

Iterator<E> iterator();

Source Link

Document

Returns an iterator over the elements in this collection.

Usage

From source file:Main.java

@Nullable
public static Class getComponentClass(Collection<?> list) {
    return isEmpty(list) ? null : list.iterator().next().getClass();
}

From source file:Main.java

/**
 * Removes nulls from provided collection.
 * /*from w  w  w  .ja  v  a  2 s.  co m*/
 * @param c
 *            to remove nulls from
 * @return number of removed elements
 */
@SuppressWarnings("rawtypes")
public static int removeNulls(Collection c) {
    int removed = 0;
    Iterator iterator = c.iterator();
    while (iterator.hasNext()) {
        if (iterator.next() == null) {
            iterator.remove();
            removed++;
        }
    }
    return removed;
}

From source file:Main.java

public static <T> T first(Collection<T> collection) {
    if (isNotEmpty(collection)) {
        return collection.iterator().next();
    }//from   w ww  . j av a 2 s .c om
    return null;
}

From source file:Main.java

public static void writeToWriter(Collection s, Writer out) throws IOException {
    writeToWriter(s.iterator(), out);
}

From source file:Main.java

public static long getSum(Collection<? extends Number> collection) {
    Iterator<? extends Number> iterator = collection.iterator();
    long sum = 0;
    while (iterator.hasNext()) {
        sum += iterator.next().longValue();
    }/*from w w w.j  a  v a 2  s  .  c o m*/

    return sum;
}

From source file:Main.java

public static <T> T find(Collection<T> collection, Predicate<T> whatToFind) {
    for (Iterator<T> iter = collection.iterator(); iter.hasNext();) {
        T item = iter.next();// w  w w  .ja v a2  s  .  c o m
        if (whatToFind.apply(item)) {
            return item;
        }
    }
    return null;
}

From source file:Main.java

/**
 * Gets one element from the provided Collection. If no element is present,
 * an Exception is thrown. No guarantee is made as to which element is
 * returned from time to time.//  w  w w. j  av a  2s.  c om
 *
 * @param <T> Collection type
 * @param collection to use
 * @return one element from the provided Collection
 * @throws NoSuchElementException if no elements are present in the
 * Collection
 */
public static <T> T getAnyFrom(Collection<T> collection) {
    final Iterator<T> iterator = collection.iterator();
    if (iterator.hasNext()) {
        return iterator.next();
    }
    throw new NoSuchElementException("No value present");
}

From source file:Main.java

public static <T> List<T> subtract(Collection<T> a, Collection<T> b) {
    ArrayList list = new ArrayList(a);
    Iterator i$ = b.iterator();

    while (i$.hasNext()) {
        Object element = i$.next();
        list.remove(element);//from   w  w  w. ja  v  a2 s.c  om
    }

    return list;
}

From source file:Main.java

/**
 * INTERNAL: Gets the first object in the collection. If the
 * collection is empty, null is returned.
 *///  w  w w.j a  v a2 s . c  o  m
public static <T> T getFirst(Collection<T> coll) {
    return (coll == null) || coll.isEmpty() ? null : coll.iterator().next();
}

From source file:Main.java

/**
 * Return first duplicate value that is not null, or null if there is no
 * such value. Even logic is similar to hasDuplicateValues, code had to be
 * duplicated because of different handling of null.
 * //from w  w  w . j ava2 s  . c  om
 * @param c
 *            to search for duplicate value
 * @return first duplicate value
 */
public static <E> E firstDuplicateValue(Collection<E> c) {
    Iterator<E> iterator = c.iterator();
    int idx = 0;
    while (iterator.hasNext()) {
        idx++;
        E e = iterator.next();
        if (e != null && iterator.hasNext()) {
            Iterator<E> subiterator = c.iterator();
            // move subiterator to index
            int sub = 0;
            while (subiterator.hasNext() && sub < idx) {
                sub++;
                subiterator.next();
            }
            // check if others are duplicates
            while (subiterator.hasNext()) {
                E s = subiterator.next();
                if (e.equals(s)) {
                    return e;
                }
            }
        }
    }
    return null;
}