Example usage for java.util Collections emptyList

Introduction

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

Prototype

@SuppressWarnings("unchecked")
public static final <T> List<T> emptyList()

Source Link

Document

Returns an empty list (immutable).

Usage

From source file:Main.java

public static <T> List<T> pageList(List<T> list, int page, int size) {
    if (page < 1) {
        throw new IllegalArgumentException("page should not little than 1,page:" + page);
    }/*  w  w w  . ja  va2s .c  o  m*/
    if (size < 1) {
        throw new IllegalArgumentException("size should not little than 1,size:" + size);
    }
    if (isEmpty(list)) {
        return Collections.emptyList();
    }
    int totalSize = list.size();

    int fromIndex = (page - 1) * size > (totalSize - 1) ? 0 : (page - 1) * size;

    int endIndex = (fromIndex + size) > (totalSize) ? (totalSize) : (fromIndex + size);

    return list.subList(fromIndex, endIndex);

}

From source file:Main.java

/**
 * /*from w ww. java2 s.c om*/
 * Returns an unmodifiable view of the specified list. This method makes use
 * of the method unmodifiableList of java.util.Collections and returns an
 * empty list if the provided list is null.
 * 
 * @param list
 * @return
 * @see java.util.Collections.unmodifiableList
 */
public static <T> List<T> unmodifiableList(List<? extends T> list) {
    if (list == null) {
        return Collections.emptyList();
    } else {
        return Collections.unmodifiableList(list);
    }
}

From source file:Main.java

public static <T> Collection<T> safe(Collection<T> l) {
    if (l == null) {
        return Collections.emptyList();
    }/*from  w w w .  j a  va  2  s .  c  o  m*/
    return l;
}

From source file:Main.java

public static <T> List<T> list() {
    return Collections.emptyList();
}

From source file:Main.java

/**
 * @return An ArrayList of the elements of array converted to strings, or the empty list if
 * array is null. Empty strings in the input array are preserved.
 *///from w ww.  j  a va2  s . c o  m
public static List<String> getStringList(JSONArray array) {
    String[] stringArray = getStringArray(array);
    if (stringArray == null) {
        return Collections.emptyList();
    }

    return Arrays.asList(stringArray);
}

From source file:Main.java

public static <O> List<O> safeSubList(List<O> l, int offset, int count) {
    if (l == null) {
        return null;
    }//from  w ww . j  a va2  s  .com

    if (offset >= l.size())
        return Collections.emptyList();

    if (count == 0)
        count = l.size();

    return l.subList(offset, Math.min(offset + count, l.size()));
}

From source file:Main.java

/**
 * Extracts a list of integer values from the specified attribute.
 * @param element        the element to fetch the integer list from
 * @param attributeName  the name of the attribute containing the integer list
 * @return a list of integer values from the specified attribute
 *//*from  ww w  .  j  a va 2s  .c o  m*/
public static List<Integer> getIntegerListAttribute(Element element, String attributeName) {
    String intListString = element.getAttribute(attributeName);
    if (intListString == null || intListString.length() == 0) {
        return Collections.emptyList();
    }

    String[] intStrings = intListString.split(" "); //$NON-NLS-1$

    List<Integer> intValues = new ArrayList<Integer>(intStrings.length);
    for (String intString : intStrings) {
        Integer intValue = Integer.valueOf(intString);
        intValues.add(intValue);
    }
    return intValues;
}

From source file:Main.java

/**
 * Generates permutations from a list of collections. Each permutation contains an element
 * from each of the collections. /*from  www  .j  a va2s. com*/
 * 
 * @param <T>         the generic type for object in the collections
 * @param collections   the list of collections
 * @return            the collection of permutations
 */
public static <T> Collection<List<T>> generatePermutations(List<Collection<T>> collections) {
    if (collections == null || collections.isEmpty()) {
        return Collections.emptyList();
    } else {
        Collection<List<T>> res = new LinkedList<List<T>>();
        permutationsImpl(collections, res, 0, new LinkedList<T>());
        return res;
    }
}

From source file:Main.java

/**
 * Create a new array list from the specified list of items. It is expected
 * that all items are of the same type.//  w  w w  . j a  va  2s. com
 * 
 * @param items
 *            The items to add to the list
 * @return
 */
public static <T> List<T> createList(T... items) {
    List<T> result;

    if (items != null && items.length > 0) {
        result = new ArrayList<T>(items.length);

        for (int i = 0; i < items.length; i++) {
            result.add(items[i]);
        }
    } else {
        result = Collections.emptyList();
    }

    return result;
}

From source file:Main.java

/**
 * This is a convenience method that essentially checks for a null list and returns Collections.emptyList in that
 * case. If the list is non-null, then this is an identity function.
 * /*from  w  w  w  .j  a  va2 s  . c om*/
 * @param <T>
 * @param list
 * @return
 */
public static <T> List<T> getListValue(List<T> list) {
    if (list == null) {
        return Collections.emptyList();
    }

    return list;
}