Example usage for java.util Collections emptySet

Introduction

In this page you can find the example usage for java.util Collections emptySet.

Prototype

@SuppressWarnings("unchecked")
public static final <T> Set<T> emptySet()

Source Link

Document

Returns an empty set (immutable).

Usage

From source file:Main.java

public static <T> Set<T> unmodifiableSet(Set<? extends T> set) {
    if (set == null) {
        return Collections.emptySet();
    } else {//  w  w  w  .  j a v  a  2 s  .  c  o m
        return Collections.unmodifiableSet(set);
    }
}

From source file:Main.java

public static <K, V> Set<V> getValueSet(Map<K, Set<V>> map, K key) {
    Set<V> values = map.get(key);
    if (values == null)
        return Collections.emptySet();

    return values;
}

From source file:Main.java

/**
 * Disables the forward and backward focus traversal keys on the given
 * component./*w  w  w  .  j a  v a 2 s. c  o m*/
 */
public static void disableFocusTraversal(Component c) {
    Set<AWTKeyStroke> emptySet = Collections.emptySet();
    c.setFocusTraversalKeys(KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, emptySet);
    c.setFocusTraversalKeys(KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, emptySet);
}

From source file:Main.java

public static <T> Set<T> copyToLinkedHashSet(Collection<? extends T> src) {
    if (src.isEmpty()) {
        return Collections.emptySet();
    }//from  www .j  ava2  s  .  co m

    return Collections.unmodifiableSet(new LinkedHashSet<T>(src));
}

From source file:Main.java

public static <T> Collection<T> nonNullCollection(final Collection<T> collection) {
    if (collection == null) {
        return Collections.emptySet();
    }/*from w  ww . j  ava2 s  .c  o m*/

    return collection;
}

From source file:Main.java

public static <T> Set<T> safe(Set<T> l) {
    if (l == null) {
        return Collections.emptySet();
    }//from ww  w.j  a  va2  s  .  co  m
    return l;
}

From source file:Main.java

/**
 * Convert to Set - this operation removes the duplicates in original list.
 * @param list//from  www .  ja v  a 2  s  .c  o  m
 * @return
 */
public static <T> Set<T> converToSet(List<T> list) {
    if (list == null || list.isEmpty()) {
        return Collections.emptySet();
    }
    return new HashSet<T>(list);
}

From source file:Main.java

/**
 * Build an set.// w w  w. j ava 2s  .  co m
 * 
 * @param values
 *            Values to be added in a set.
 * @return A set containing all given values.
 */
@SafeVarargs
public static <T> Set<T> asSet(T... values) {
    if (values == null || values.length == 0) {
        return Collections.emptySet();
    } else {
        // A lit bit higher than load factor
        int size = (int) Math.floor(values.length * 1.4);
        Set<T> set = new HashSet<>(size);
        for (T value : values) {
            set.add(value);
        }

        return set;
    }
}

From source file:Main.java

public static <T> Set<T> toImmutableSet(Set<T> set) {
    switch (set.size()) {
    case 0:/*from  w w  w.java2 s .com*/
        return Collections.emptySet();
    case 1:
        return Collections.singleton(set.iterator().next());
    default:
        return Collections.unmodifiableSet(set);
    }
}

From source file:Main.java

/**
 * Returns an non null value based on the giving {@link Set}
 *
 * @param set//from   w  ww  .jav  a  2 s  .  co  m
 *            value to evaluate
 * @return the original value or an empty {@link Set}
 * @since 4.2
 */
public static <T> Set<T> nonNullSet(@Nullable final Set<T> set) {
    return set == null ? Collections.emptySet() : set;
}