Example usage for java.util Collection size

Introduction

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

Prototype

int size();

Source Link

Document

Returns the number of elements in this collection.

Usage

From source file:Main.java

public static <T> T[] toTypedArray(Collection<?> collection, Class<T> type) {
    @SuppressWarnings("unchecked")
    T[] array = (T[]) Array.newInstance(type, collection.size());
    Object[] data = collection.toArray();
    for (int i = 0; i < array.length; i++) {
        array[i] = type.cast(data[i]);/*from  w  ww.  ja  va  2s . c  om*/
    }
    return array;

}

From source file:Main.java

/**
 * Convert collection to array. This is a bit cleaner version of
 * {@link Collection#toArray(Object[])}.
 *//*from w ww  . j av a2 s.  c o  m*/
@SuppressWarnings("unchecked")
public static <T> T[] toArray(Collection<? extends T> collection, Class<T> type) {
    T[] result = (T[]) java.lang.reflect.Array.newInstance(type, collection.size());

    Iterator<? extends T> it = collection.iterator();
    for (int i = 0; i < collection.size(); i++) {
        result[i] = it.next();
    }

    return result;
}

From source file:Main.java

/**
 * Returns an array containing all of the elements of the
 * Iterator//from   w w  w  .  jav  a  2s .  c  om
 * @param iterator Iterator to copy the contexts of
 * @return an array containing a copy of the iterator contents
 */
public static <T> T[] toArray(Iterator<? extends T> iterator, Class<T> type) {
    if (iterator.hasNext()) {
        Collection arrayList = arrayList(iterator);
        T[] outArray = (T[]) Array.newInstance(type, arrayList.size());

        return (T[]) arrayList.toArray(outArray);
    } else {
        // optimize empty iterator case
        return (T[]) Array.newInstance(type, 0);
    }
}

From source file:Main.java

/**
 * Enforce that a Collection contains no more than one element and return that element
 * if it exists.//from   www  . j a v a  2 s .c om
 * 
 * @param collection the Collection to examine
 * @return null if the Collection is null or empty, the Collection's single object if
 *       its size is one, or throw if its size is greater than one.
 * @throws IllegalArgumentException if the Collection contains more than one element
 */
public static <T> T singleObject(Collection<T> collection) {
    if (collection == null || collection.isEmpty())
        return null;
    if (collection.size() > 1)
        throw new IllegalArgumentException("more than one element in collection");
    return collection.iterator().next();
}

From source file:org.springframework.cloud.vault.VaultErrorMessage.java

/**
 * Obtain the error message from a JSON response.
 * /*from   ww  w . ja v  a 2 s  . c o m*/
 * @param json
 * @return
 */
static String getError(String json) {

    if (json.contains("\"errors\":")) {

        try {
            Map<String, Object> map = OBJECT_MAPPER.readValue(json.getBytes(), Map.class);
            if (map.containsKey("errors")) {

                Collection<String> errors = (Collection<String>) map.get("errors");
                if (errors.size() == 1) {
                    return errors.iterator().next();
                }
                return errors.toString();
            }

        } catch (IOException o_O) {
            // ignore
        }
    }
    return json;
}

From source file:Main.java

public static <T> List<T> appendAllList(List<T> list, Collection<? extends T> c) {
    if (list == null) {
        list = new ArrayList<T>(1);
    }/*w ww. ja va2 s .  c  o m*/
    if (c != null && c.size() > 0) {
        list.addAll(c);
    }
    return list;
}

From source file:Main.java

/**
 * Ensures that all elements of the given collection can be cast to a desired type.
 * /*from ww  w  . j a  v  a2s .  c o m*/
 * @param collection the collection to check
 * @param type the desired type
 * @return a collection of the desired type
 * @throws ClassCastException if an element cannot be cast to the desired type
 */
@SuppressWarnings("unchecked")
public static <E> Collection<E> checkCollection(Collection<?> collection, Class<E> type) {
    if (DEBUG) {
        Collection<E> copy = new ArrayList<E>(collection.size());
        for (Object element : collection) {
            copy.add(type.cast(element));
        }
        return copy;
    }
    return (Collection<E>) collection;
}

From source file:Main.java

public static long[] toPrimitive(Collection<Long> collection) {
    if (isEmpty(collection)) {
        return new long[0];
    }/*from   w  w  w.j  ava 2s  .  com*/

    long[] array = new long[collection.size()];
    int i = 0;
    for (Long val : collection) {
        array[i] = val;
        i++;
    }
    return array;
}

From source file:Main.java

public static <T extends Object> int countIntersection(Collection<? extends T> s1, Collection<? extends T> s2) {
    if (s1 == null || s2 == null)
        return 0;
    int n1 = s1.size();
    int n2 = s2.size();
    if (n2 < n1) {
        Collection<? extends T> t = s1;
        s1 = s2;//from   w w w  .  j ava2 s.  com
        s2 = t;
    }
    int n = 0;
    for (T e : s1) {
        if (s2.contains(e))
            n++;
    }
    return n;
}

From source file:Main.java

/**
 * Converts the <code>collection</code> into an array
 * using the <code>generator</code> to create the array
 * without creating a <code>Stream</code> on the collection.
 *
 * @param collection The collection to be converted
 * @param generator The generator to create the empty array
 * @param <T> The type of the elements
 *
 * @return An array with the length of the <code>collection</code>
 * containing all elements of the <code>collection</code>
 *
 * @throws NullPointerException if either <code>collection</code>
 * or <code>generator</code> is <code>null</code>
 *///from w  w w . j  a  va 2 s. co  m
public static <T> T[] toArray(Collection<T> collection, IntFunction<T[]> generator)
        throws NullPointerException {
    return collection.toArray(generator.apply(collection.size()));
}