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

/**
 * Creates a map with the elements of the collection as values using the
 * specified keyMethod to obtain the key from the elements.
 *///from ww  w  .  j a va  2s.  c  o  m
@SuppressWarnings("unchecked")
public static <K, T> Map<K, T> createMap(Collection<T> collection, String keyMethod) {
    Map<K, T> map = new HashMap<>(collection.size());

    if (collection.isEmpty()) {
        return map;
    }

    Class<?> elementClass = collection.iterator().next().getClass();

    Method getKeyMethod;

    try {
        getKeyMethod = elementClass.getMethod(keyMethod, new Class[0]);
    } catch (Exception e) {
        throw new RuntimeException("Failed to get key method", e);
    }

    for (T element : collection) {
        K key;
        try {
            key = (K) getKeyMethod.invoke(element, (Object[]) null);
        } catch (Exception e) {
            throw new RuntimeException("Failed to get key", e);
        }

        map.put(key, element);
    }

    return map;
}

From source file:Main.java

/**
 * Returns <code>true</code> iff at least one element is in both collections15.
 * <p/>/*from   w  ww .ja v  a 2  s .co  m*/
 * In other words, this method returns <code>true</code> iff the
 * {@link #intersection} of <i>coll1</i> and <i>coll2</i> is not empty.
 *
 * @param coll1 the first collection, must not be null
 * @param coll2 the first collection, must not be null
 * @return <code>true</code> iff the intersection of the collections15 is non-empty
 * @see #intersection
 * @since 2.1
 */
public static <E> boolean containsAny(final Collection<? extends E> coll1,
        final Collection<? extends E> coll2) {
    if (coll1.size() < coll2.size()) {
        for (Iterator it = coll1.iterator(); it.hasNext();) {
            if (coll2.contains(it.next())) {
                return true;
            }
        }
    } else {
        for (Iterator it = coll2.iterator(); it.hasNext();) {
            if (coll1.contains(it.next())) {
                return true;
            }
        }
    }
    return false;
}

From source file:Main.java

/**
 * Returns <code>true</code> iff all elements of {@code coll2} are also contained
 * in {@code coll1}. The cardinality of values in {@code coll2} is not taken into account,
 * which is the same behavior as {@link Collection#containsAll(Collection)}.
 * <p>/*from  w w w  .j  a  v  a 2s  .com*/
 * In other words, this method returns <code>true</code> iff the
 * {@link #intersection} of <i>coll1</i> and <i>coll2</i> has the same cardinality as
 * the set of unique values from {@code coll2}. In case {@code coll2} is empty, {@code true}
 * will be returned.
 * <p>
 * This method is intended as a replacement for {@link Collection#containsAll(Collection)}
 * with a guaranteed runtime complexity of {@code O(n + m)}. Depending on the type of
 * {@link Collection} provided, this method will be much faster than calling
 * {@link Collection#containsAll(Collection)} instead, though this will come at the
 * cost of an additional space complexity O(n).
 *
 * @param coll1  the first collection, must not be null
 * @param coll2  the second collection, must not be null
 * @return <code>true</code> iff the intersection of the collections has the same cardinality
 *   as the set of unique elements from the second collection
 * @since 4.0
 */
public static boolean containsAll(final Collection<?> coll1, final Collection<?> coll2) {
    if (coll2.isEmpty()) {
        return true;
    } else {
        final Iterator<?> it = coll1.iterator();
        final Set<Object> elementsAlreadySeen = new HashSet<Object>();
        for (final Object nextElement : coll2) {
            if (elementsAlreadySeen.contains(nextElement)) {
                continue;
            }

            boolean foundCurrentElement = false;
            while (it.hasNext()) {
                final Object p = it.next();
                elementsAlreadySeen.add(p);
                if (nextElement == null ? p == null : nextElement.equals(p)) {
                    foundCurrentElement = true;
                    break;
                }
            }

            if (foundCurrentElement) {
                continue;
            } else {
                return false;
            }
        }
        return true;
    }
}

From source file:com.projity.grouping.core.model.NodeModelUtil.java

private static void extractNodeList(NodeModel nodeModel, Node parent, Collection result) {
    if (parent != null)
        result.add(parent);//  ww  w .ja  v  a2  s . c o  m
    Collection children = nodeModel.getChildren(parent);
    if (children != null) {
        Iterator i = children.iterator();
        while (i.hasNext()) {
            Node n = (Node) i.next();
            extractNodeList(nodeModel, n, result);
        }
    }
}

From source file:Main.java

/**
 * /*  w w w .ja v a  2s .co m*/
 * @param collection
 * @return float[]
 */
public static float[] toFloatArray(final Collection<Float> collection) {
    final float[] array = new float[collection == null ? 0 : collection.size()];

    if (collection != null) {
        int i = 0;

        for (Iterator<Float> iterator = collection.iterator(); iterator.hasNext();) {
            array[i++] = iterator.next().floatValue();
        }
    }

    return array;
}

From source file:Main.java

public static String join(Collection<?> input, String sep) {
    if (input == null || input.size() == 0) {
        return "";
    }/*from www . j av  a 2s. co  m*/
    StringBuilder sb = new StringBuilder();
    int index = 0;
    int size = input.size();
    Iterator<?> it = input.iterator();
    while (it.hasNext()) {
        if (index == size - 1) {
            break;
        }
        Object o = it.next();
        sb.append(o).append(sep);
        index++;
    }
    sb.append(it.next());
    return sb.toString();
}

From source file:com.projity.grouping.core.model.NodeModelUtil.java

private static void dumpTask(NodeModel nodeModel, Node parent, String indent) {
    if (parent != null)
        System.out.println(indent + ">" + parent.toString());
    Collection children = nodeModel.getChildren(parent);
    if (children != null) {
        Iterator i = children.iterator();
        while (i.hasNext()) {
            Node n = (Node) i.next();
            Object impl = n.getImpl();
            if (impl instanceof Task) {
                if (((Task) impl).getWbsParentTask() != (parent == null ? null : parent.getImpl()))
                    System.out.println("cached hierarchy error - child " + impl + " cached parent"
                            + ((Task) impl).getWbsParentTask() + " parent " + parent.getImpl());
            }/*from   w w  w  . jav a2 s.  co  m*/
            dumpTask(nodeModel, n, indent + "--");
        }
    }
}

From source file:edu.uci.ics.jung.utils.PredicateUtils.java

/**
 * Returns <code>true</code> if all elements of <code>c</code>
 * satisfy <code>p</code>./*from  w  w w .  j a va2s .  c  o m*/
 */
public static boolean satisfiesPredicate(Collection c, Predicate p) {
    for (Iterator iter = c.iterator(); iter.hasNext();) {
        if (!p.evaluate(iter.next()))
            return false;
    }
    return true;
}

From source file:Main.java

/**
 * Constructs a single String by iterating over the elements in the
 * collection parameter, calling toString() on each method.
 * //  w  w  w.j a va  2s.  c o  m
 * @param <T>
 * @param collection
 * @param separator
 * @return A separator-separated value String.
 */
public static <T extends Object> String toXsvString(Collection<T> collection, String separator) {
    if (collection == null) {
        return null;
    }

    StringBuffer sb = new StringBuffer();

    int count = 0;
    for (Iterator<T> iter = collection.iterator(); iter.hasNext(); count++) {
        if (count > 0) {
            sb.append(separator);
        }
        sb.append(iter.next().toString());
    }

    return sb.toString();
}

From source file:Main.java

public static <T> T checkAndReturnOnlyElement(Collection<T> collection) {
    if (collection == null || collection.size() == 0) {
        return null;
    } else if (collection.size() != 1) {
        throw new IllegalStateException("collection size is " + collection.size());
    }//from w  w w .ja  va 2 s . c om
    return collection.iterator().next();
}