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

/**
 * Get comma separated string from collection
 * /* w  ww.j  a v  a  2  s  .c o  m*/
 * @param strings
 * @return
 */
public static String getCommaSeparatedString(Collection<String> strings) {
    if (strings != null && !strings.isEmpty()) {
        Iterator<String> it = strings.iterator();
        StringBuilder sb = new StringBuilder(it.next());
        while (it.hasNext()) {
            sb.append("," + it.next());
        }
        return sb.toString();
    } else {
        return null;
    }
}

From source file:Main.java

public static String join(Collection<?> coll, String delimiter) {
    if (coll.isEmpty()) {
        return "";
    }// w  w w  .ja  va  2  s .  com
    Iterator<?> it = coll.iterator();
    String s = String.valueOf(it.next());
    while (it.hasNext()) {
        s += delimiter;
        s += String.valueOf(it.next());
    }
    return s;
}

From source file:Main.java

/**
 * Creates new collection that contains only element whose string
 * representation starts with prefix It is parameterized.
 * // w  w  w.  j a  v  a2 s. com
 * @param c
 *            raw collection to create prefixed collection from
 * @param prefix
 *            to use as filter
 * @return collection without nulls
 */
public static <T> Collection<T> withPrefix(Collection<T> c, String prefix) {
    Collection<T> prefixed = new ArrayList<T>();
    Iterator<T> iterator = c.iterator();
    while (iterator.hasNext()) {
        T o = iterator.next();
        if (o != null && o.toString().startsWith(prefix)) {
            prefixed.add(o);
        }
    }
    return prefixed;
}

From source file:Main.java

public static Object findFirstMatch(Collection source, Collection candidates) {
    if (!isEmpty(source) && !isEmpty(candidates)) {
        Iterator it = candidates.iterator();

        Object candidate;/*from w ww .ja v a 2 s .c  o  m*/
        do {
            if (!it.hasNext()) {
                return null;
            }

            candidate = it.next();
        } while (!source.contains(candidate));

        return candidate;
    } else {
        return null;
    }
}

From source file:Main.java

public static <K, V> Map<K, V> collectionToMap(Collection<V> collection, String key) {
    Map<K, V> map = null;/*from w  ww .  j  a  v a 2s .c o  m*/
    Iterator<V> iterator = collection.iterator();
    try {
        if (key == null)
            throw new Exception("no key filed");
        else {
            map = new HashMap<K, V>();
            while (iterator.hasNext()) {
                V v = iterator.next();
                Class<? extends Object> c = v.getClass();
                Field field = c.getField(key);
                field.setAccessible(true);
                map.put((K) field.get(v), v);
            }
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
    return map;
}

From source file:Main.java

public static Collection intersection(Collection a, Collection b)

{

    Collection results = new HashSet();

    for (Iterator i = a.iterator(); i.hasNext();) {

        Object o = i.next();//from   ww  w. jav a  2  s.  co  m

        if (b.contains(o)) {

            results.add(o);

        }

    }

    return results;

}

From source file:Main.java

/**
 * Return the first element of the collection.
 *
 * @param collection The collection.//from w w w  .  j a v a2s. co m
 * @param <T>        The objects stored in the collection.
 *
 * @return The first element of the collection or null if the collection is empty.
 */
public static <T> T first(Collection<T> collection) {
    if (collection.isEmpty()) {
        return null;
    }

    return collection.iterator().next();
}

From source file:com.apextom.util.CollectionUtil.java

/**
 * ? null .//from ww  w. java  2 s . co  m
 * 
 * @param list
 */
public static void removeNull(Collection<Object> list) {
    if (list == null || list.size() == 0) {
        return;
    }
    Iterator<Object> iter = list.iterator();
    while (iter.hasNext()) {
        if (iter.next() == null) {
            iter.remove();
        }
    }

}

From source file:Main.java

/**
 * Check whether the given Collection contains the given element instance.
 * <p>Enforces the given instance to be present, rather than returning
 * <code>true</code> for an equal element as well.
 * @param collection the Collection to check
 * @param element the element to look for
 * @return <code>true</code> if found, <code>false</code> else
 *//*from   w  ww . j  a  va2  s.  co  m*/
public static boolean containsInstance(Collection<?> collection, Object element) {
    if (collection != null) {
        for (Iterator<?> it = collection.iterator(); it.hasNext();) {
            Object candidate = it.next();
            if (candidate == element) {
                return true;
            }
        }
    }
    return false;
}

From source file:Main.java

public static boolean isEmptyCollection(Collection<?> cols) {
    if (cols == null || cols.isEmpty()) {
        return true;
    }//from   w  w w. ja va 2 s  .  co  m
    Iterator<?> ite = cols.iterator();
    while (ite.hasNext()) {
        if (ite.next() == null) {
            return true;
        }
    }
    return false;
}