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

/**
 * Returns an unmodifiable set containing the given elements.
 *
 * @param ts the elements from which to create a set
 * @param <T> the type of the element in the set
 * @return an unmodifiable set containing the given elements or {@code null} in case the given element array is
 * {@code null}.//from w  ww.j  a v a 2  s. c om
 */
public static <T> Set<T> asSet(T... ts) {
    if (ts == null) {
        return null;
    } else if (ts.length == 0) {
        return Collections.emptySet();
    } else {
        Set<T> set = new HashSet<T>(ts.length);
        Collections.addAll(set, ts);
        return Collections.unmodifiableSet(set);
    }
}

From source file:Main.java

public static <T> Set<T> nonNullFrom(Set<T> set) {
    if (set == null || set.isEmpty()) {
        return Collections.emptySet();
    }/*  w  w w  .ja  v  a  2  s .  co  m*/
    return Collections.unmodifiableSet(set);
}

From source file:Main.java

@SafeVarargs
public static <T> Set<T> newSet(T... values) {
    if (values == null) {
        return Collections.emptySet();
    }//  w w w.  j  a va  2 s .  co  m

    return new HashSet<>(Arrays.asList(values));
}

From source file:Main.java

public static Set<String> getQueryParameterNames(Uri uri) {
    String query = uri.getEncodedQuery();
    if (query == null) {
        return Collections.emptySet();
    }//from   w ww  .  ja  va 2s. c o m

    Set<String> names = new LinkedHashSet<String>();
    int start = 0;
    do {
        int next = query.indexOf('&', start);
        int end = (next == -1) ? query.length() : next;

        int separator = query.indexOf('=', start);
        if (separator > end || separator == -1) {
            separator = end;
        }

        String name = query.substring(start, separator);
        names.add(uri.decode(name));

        // Move start to end of name.
        start = end + 1;
    } while (start < query.length());

    return Collections.unmodifiableSet(names);
}

From source file:Main.java

public static Set getSet(Object... objs) {
    if (objs.length == 0) {
        return Collections.emptySet();
    } else if (objs.length == 1) {
        return Collections.singleton(objs[0]);
    } else {//w  ww. java  2  s. c  o  m
        return new HashSet(Arrays.asList(objs));
    }

}

From source file:Main.java

public static <E> Set<E> asSet(E... elements) {
    if (elements == null || elements.length == 0) {
        return Collections.emptySet();
    }/*from   ww  w . j ava  2s.  com*/

    if (elements.length == 1) {
        return Collections.singleton(elements[0]);
    }

    LinkedHashSet<E> set = new LinkedHashSet<E>(elements.length * 4 / 3 + 1);
    Collections.addAll(set, elements);
    return set;
}

From source file:Main.java

/**
 * Convert a char array to a unmodifiable Set.
 *
 * @param array the contents of the new Set
 * @return a unmodifiable Set containing the elements in the array.
 *//*w  w w . j  ava 2 s  .  com*/
public static Set<Character> arrayToUnmodifiableSet(char... array) {
    if (array == null) {
        return Collections.emptySet();
    }
    if (array.length == 1) {
        return Collections.singleton(array[0]);
    }
    return Collections.unmodifiableSet(arrayToSet(array));
}

From source file:Main.java

/**
 * Convert a String to a unmodifiable set of characters.
 *
 * @param str The string to convert/*from   w  w  w . j ava  2 s .  c om*/
 * @return A set containing the characters in str. A empty set is returned if str is null.
 */
public static Set<Character> strToUnmodifiableSet(String str) {
    if (str == null) {
        return Collections.emptySet();
    }
    if (str.length() == 1) {
        return Collections.singleton(str.charAt(0));
    }
    return Collections.unmodifiableSet(strToSet(str));
}

From source file:Main.java

public static <T> Set<T> nullToEmpty(Set<T> set) {
    return set == null ? Collections.emptySet() : set;
}

From source file:Main.java

/**
 * Converts the specified {@link JSONArray JSON array} to a
 * {@link List list}./*from ww  w  . ja v  a 2s.  c o  m*/
 *
 * @param <T> the type of elements maintained by the specified json array
 * @param jsonArray the specified json array
 * @return an {@link ArrayList array list}
 */
@SuppressWarnings("unchecked")
public static <T> Set<T> jsonArrayToSet(final JSONArray jsonArray) {
    if (null == jsonArray) {
        return Collections.emptySet();
    }

    final Set<T> ret = new HashSet<T>();

    for (int i = 0; i < jsonArray.length(); i++) {
        ret.add((T) jsonArray.opt(i));
    }

    return ret;
}