io.jsonwebtoken.lang.Collections Maven / Gradle / Ivy
/*
* Copyright (C) 2014 jsonwebtoken.io
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.jsonwebtoken.lang;
import java.util.Arrays;
import java.util.*;
public final class Collections {
private Collections(){} //prevent instantiation
/**
* Return true if the supplied Collection is null
* or empty. Otherwise, return false.
* @param collection the Collection to check
* @return whether the given Collection is empty
*/
public static boolean isEmpty(Collection collection) {
return (collection == null || collection.isEmpty());
}
/**
* Returns the collection's size or {@code 0} if the collection is {@code null}.
*
* @param collection the collection to check.
* @return the collection's size or {@code 0} if the collection is {@code null}.
* @since 0.9.2
*/
public static int size(Collection collection) {
return collection == null ? 0 : collection.size();
}
/**
* Returns the map's size or {@code 0} if the map is {@code null}.
*
* @param map the map to check
* @return the map's size or {@code 0} if the map is {@code null}.
* @since 0.9.2
*/
public static int size(Map map) {
return map == null ? 0 : map.size();
}
/**
* Return true if the supplied Map is null
* or empty. Otherwise, return false.
* @param map the Map to check
* @return whether the given Map is empty
*/
public static boolean isEmpty(Map map) {
return (map == null || map.isEmpty());
}
/**
* Convert the supplied array into a List. A primitive array gets
* converted into a List of the appropriate wrapper type.
* A null source value will be converted to an
* empty List.
* @param source the (potentially primitive) array
* @return the converted List result
* @see Objects#toObjectArray(Object)
*/
public static List arrayToList(Object source) {
return Arrays.asList(Objects.toObjectArray(source));
}
/**
* Merge the given array into the given Collection.
* @param array the array to merge (may be null)
* @param collection the target Collection to merge the array into
*/
@SuppressWarnings("unchecked")
public static void mergeArrayIntoCollection(Object array, Collection collection) {
if (collection == null) {
throw new IllegalArgumentException("Collection must not be null");
}
Object[] arr = Objects.toObjectArray(array);
for (Object elem : arr) {
collection.add(elem);
}
}
/**
* Merge the given Properties instance into the given Map,
* copying all properties (key-value pairs) over.
*
Uses Properties.propertyNames() to even catch
* default properties linked into the original Properties instance.
* @param props the Properties instance to merge (may be null)
* @param map the target Map to merge the properties into
*/
@SuppressWarnings("unchecked")
public static void mergePropertiesIntoMap(Properties props, Map map) {
if (map == null) {
throw new IllegalArgumentException("Map must not be null");
}
if (props != null) {
for (Enumeration en = props.propertyNames(); en.hasMoreElements();) {
String key = (String) en.nextElement();
Object value = props.getProperty(key);
if (value == null) {
// Potentially a non-String value...
value = props.get(key);
}
map.put(key, value);
}
}
}
/**
* Check whether the given Iterator contains the given element.
* @param iterator the Iterator to check
* @param element the element to look for
* @return true if found, false else
*/
public static boolean contains(Iterator iterator, Object element) {
if (iterator != null) {
while (iterator.hasNext()) {
Object candidate = iterator.next();
if (Objects.nullSafeEquals(candidate, element)) {
return true;
}
}
}
return false;
}
/**
* Check whether the given Enumeration contains the given element.
* @param enumeration the Enumeration to check
* @param element the element to look for
* @return true if found, false else
*/
public static boolean contains(Enumeration enumeration, Object element) {
if (enumeration != null) {
while (enumeration.hasMoreElements()) {
Object candidate = enumeration.nextElement();
if (Objects.nullSafeEquals(candidate, element)) {
return true;
}
}
}
return false;
}
/**
* Check whether the given Collection contains the given element instance.
*
Enforces the given instance to be present, rather than returning
* true for an equal element as well.
* @param collection the Collection to check
* @param element the element to look for
* @return true if found, false else
*/
public static boolean containsInstance(Collection collection, Object element) {
if (collection != null) {
for (Object candidate : collection) {
if (candidate == element) {
return true;
}
}
}
return false;
}
/**
* Return true if any element in 'candidates' is
* contained in 'source'; otherwise returns false.
* @param source the source Collection
* @param candidates the candidates to search for
* @return whether any of the candidates has been found
*/
public static boolean containsAny(Collection source, Collection candidates) {
if (isEmpty(source) || isEmpty(candidates)) {
return false;
}
for (Object candidate : candidates) {
if (source.contains(candidate)) {
return true;
}
}
return false;
}
/**
* Return the first element in 'candidates' that is contained in
* 'source'. If no element in 'candidates' is present in
* 'source' returns null. Iteration order is
* {@link Collection} implementation specific.
* @param source the source Collection
* @param candidates the candidates to search for
* @return the first present object, or null if not found
*/
public static Object findFirstMatch(Collection source, Collection candidates) {
if (isEmpty(source) || isEmpty(candidates)) {
return null;
}
for (Object candidate : candidates) {
if (source.contains(candidate)) {
return candidate;
}
}
return null;
}
/**
* Find a single value of the given type in the given Collection.
* @param collection the Collection to search
* @param type the type to look for
* @param the generic type parameter for {@code type}
* @return a value of the given type found if there is a clear match,
* or null if none or more than one such value found
*/
@SuppressWarnings("unchecked")
public static T findValueOfType(Collection collection, Class type) {
if (isEmpty(collection)) {
return null;
}
T value = null;
for (Object element : collection) {
if (type == null || type.isInstance(element)) {
if (value != null) {
// More than one value found... no clear single value.
return null;
}
value = (T) element;
}
}
return value;
}
/**
* Find a single value of one of the given types in the given Collection:
* searching the Collection for a value of the first type, then
* searching for a value of the second type, etc.
* @param collection the collection to search
* @param types the types to look for, in prioritized order
* @return a value of one of the given types found if there is a clear match,
* or null if none or more than one such value found
*/
public static Object findValueOfType(Collection collection, Class[] types) {
if (isEmpty(collection) || Objects.isEmpty(types)) {
return null;
}
for (Class type : types) {
Object value = findValueOfType(collection, type);
if (value != null) {
return value;
}
}
return null;
}
/**
* Determine whether the given Collection only contains a single unique object.
* @param collection the Collection to check
* @return true if the collection contains a single reference or
* multiple references to the same instance, false else
*/
public static boolean hasUniqueObject(Collection collection) {
if (isEmpty(collection)) {
return false;
}
boolean hasCandidate = false;
Object candidate = null;
for (Object elem : collection) {
if (!hasCandidate) {
hasCandidate = true;
candidate = elem;
}
else if (candidate != elem) {
return false;
}
}
return true;
}
/**
* Find the common element type of the given Collection, if any.
* @param collection the Collection to check
* @return the common element type, or null if no clear
* common type has been found (or the collection was empty)
*/
public static Class findCommonElementType(Collection collection) {
if (isEmpty(collection)) {
return null;
}
Class candidate = null;
for (Object val : collection) {
if (val != null) {
if (candidate == null) {
candidate = val.getClass();
}
else if (candidate != val.getClass()) {
return null;
}
}
}
return candidate;
}
/**
* Marshal the elements from the given enumeration into an array of the given type.
* Enumeration elements must be assignable to the type of the given array. The array
* returned will be a different instance than the array given.
* @param enumeration the collection to convert to an array
* @param array an array instance that matches the type of array to return
* @param the element type of the array that will be created
* @param the element type contained within the enumeration.
* @return a new array of type {@code A} that contains the elements in the specified {@code enumeration}.
*/
public static A[] toArray(Enumeration enumeration, A[] array) {
ArrayList elements = new ArrayList();
while (enumeration.hasMoreElements()) {
elements.add(enumeration.nextElement());
}
return elements.toArray(array);
}
/**
* Adapt an enumeration to an iterator.
* @param enumeration the enumeration
* @param the type of elements in the enumeration
* @return the iterator
*/
public static Iterator toIterator(Enumeration enumeration) {
return new EnumerationIterator(enumeration);
}
/**
* Iterator wrapping an Enumeration.
*/
private static class EnumerationIterator implements Iterator {
private Enumeration enumeration;
public EnumerationIterator(Enumeration enumeration) {
this.enumeration = enumeration;
}
public boolean hasNext() {
return this.enumeration.hasMoreElements();
}
public E next() {
return this.enumeration.nextElement();
}
public void remove() throws UnsupportedOperationException {
throw new UnsupportedOperationException("Not supported");
}
}
}