Example usage for java.util Collection isEmpty

Introduction

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

Prototype

boolean isEmpty();

Source Link

Document

Returns true if this collection contains no elements.

Usage

From source file:Main.java

/**
 * Create a textual representation of the given collection, separating the individual elements by the provided separator.
 * //  ww w  .j  av a  2s.c o  m
 * @param collection
 *            the collection to represent as text
 * @param separator
 *            the separator to include between elements of the collection
 * @return the colleciton's textual representation (or an empty String if the collection is {@code null} or empty)
 */
public static String toString(final Collection<?> collection, final String separator) {
    if (collection == null || collection.isEmpty()) {
        // just return an empty String if the collection is null or empty
        return "";
    }
    if (separator == null) {
        // fall back to the collection's toString() method if no custom separator has been specified
        return collection.toString();
    }
    // guess at a meaningful initial size
    final StringBuilder builder = new StringBuilder(collection.size() * (16 + separator.length()));
    boolean addSeparator = false;
    // iterate over the individual elements
    for (final Object collectionElement : collection) {
        if (addSeparator) {
            builder.append(separator);
        } else {
            addSeparator = true;
        }
        // null elements are treated as empty Strings
        if (collectionElement != null) {
            builder.append(collectionElement.toString());
        }
    }
    return builder.toString();
}

From source file:Main.java

public static boolean isEmpty(Collection collection) {
    System.out.println("3333333333333333333333");
    return (collection == null) || collection.isEmpty();
}

From source file:Main.java

public static Map groupMap(Collection collection, String keyName) {
    Map map = new HashMap();
    if (collection == null || collection.isEmpty()) {
        return map;
    }//from   w  ww .j  ava  2  s .c  o  m

    Map eachMap = null;
    Object key = null;
    List groupList = null;

    Iterator iter = collection.iterator();

    while (iter.hasNext()) {
        eachMap = (Map) iter.next();
        key = eachMap.get(keyName);
        if (key == null) {
            continue;
        }
        if (map.containsKey(key)) {
            groupList = (List) map.get(key);
            groupList.add(eachMap);
        } else {
            groupList = new ArrayList();
            groupList.add(eachMap);
            map.put(key, groupList);
        }
    }
    return map;
}

From source file:Main.java

public static <E extends Comparable<E>> E getSmallest(final Collection<? extends E> c) {
    if (c.isEmpty()) {
        throw new NoSuchElementException();
    }//from   ww w .  ja  v a2  s.  c  o  m

    if ((c instanceof List) && (c instanceof RandomAccess)) {
        return getSmallest((List<? extends E>) c);
    }

    final Iterator<? extends E> iterator = c.iterator();
    E result = iterator.next();
    E element;

    while (iterator.hasNext()) {
        element = iterator.next();
        if (element.compareTo(result) < 0) {
            result = element;
        }
    }

    return result;
}

From source file:Main.java

public static <E> E getSmallest(final Comparator<? super E> comparator, final Collection<? extends E> c) {
    if (c.isEmpty()) {
        throw new NoSuchElementException();
    }/* w ww .jav a2  s .c  o m*/

    if ((c instanceof List) && (c instanceof RandomAccess)) {
        return getSmallest(comparator, (List<? extends E>) c);
    }

    final Iterator<? extends E> iterator = c.iterator();
    E result = iterator.next();
    E element;

    while (iterator.hasNext()) {
        element = iterator.next();
        if (comparator.compare(element, result) < 0) {
            result = element;
        }
    }

    return result;
}

From source file:Main.java

public static <E extends Comparable<E>> E getGreatest(final Collection<? extends E> c) {
    if (c.isEmpty()) {
        throw new NoSuchElementException();
    }/*ww  w.  j  a  v a  2  s .  c om*/

    if ((c instanceof List) && (c instanceof RandomAccess)) {
        return getGreatest((List<? extends E>) c);
    }

    final Iterator<? extends E> iterator = c.iterator();
    E result = iterator.next();
    E element;

    while (iterator.hasNext()) {
        element = iterator.next();
        if (element.compareTo(result) > 0) {
            result = element;
        }
    }

    return result;
}

From source file:Main.java

public static <E> E getGreatest(final Comparator<? super E> comparator, final Collection<? extends E> c) {
    if (c.isEmpty()) {
        throw new NoSuchElementException();
    }/*from   www  .  j  a v a 2s  . c  o  m*/

    if ((c instanceof List) && (c instanceof RandomAccess)) {
        return getGreatest(comparator, (List<? extends E>) c);
    }

    final Iterator<? extends E> iterator = c.iterator();
    E result = iterator.next();
    E element;

    while (iterator.hasNext()) {
        element = iterator.next();
        if (comparator.compare(element, result) > 0) {
            result = element;
        }
    }

    return result;
}

From source file:Main.java

public static boolean isEmpty(Collection<?> items) {
    if (items == null) {
        return true;
    }//  w w  w  . ja v  a 2s. c  o m
    return items.isEmpty();
}

From source file:com.romeikat.datamessie.core.base.ui.component.DocumentsFilter.java

private static String generateDocumentsString(final Collection<Long> documentIds) {
    if (documentIds == null || documentIds.isEmpty()) {
        return null;
    }/*w  ww  .  j  a va 2s. com*/
    final String documentsString = StringUtils.join(documentIds, " ");
    return documentsString;
}

From source file:Main.java

/**
 * Returns a list of the elements invoking toString on non-null elements.
 * @param collection to render// w  ww .  j a v  a 2s.  c om
 * @param <T> type
 * @return comma-separate list of values (no escape)
 */
public static <T> String toString(Collection<T> collection) {
    if (collection == null) {
        return "null";
    }
    if (collection.isEmpty()) {
        return "";
    }
    StringBuilder buf = new StringBuilder();
    String delimiter = "";
    for (T t : collection) {
        if (t == null) {
            continue;
        }
        buf.append(delimiter);
        buf.append(t);
        delimiter = ", ";
    }
    return buf.toString();
}