com.firefly.utils.CollectionUtils Maven / Gradle / Ivy
package com.firefly.utils;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Properties;
/**
* Miscellaneous collection utility methods. Mainly for internal use within the
* framework.
*/
public abstract class CollectionUtils {
/**
* Return {@code true} if the supplied Collection is {@code null} or empty.
* Otherwise, return {@code 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());
}
/**
* Return {@code true} if the supplied Map is {@code null} or empty.
* Otherwise, return {@code 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.
*
* NOTE: Generally prefer the standard {@link Arrays#asList} method.
* This {@code arrayToList} method is just meant to deal with an incoming
* Object value that might be an {@code Object[]} or a primitive array at
* runtime.
*
* A {@code null} source value will be converted to an empty List.
*
* @param source
* the (potentially primitive) array
* @return the converted List result
* @see ObjectUtils#toObjectArray(Object)
* @see Arrays#asList(Object[])
*/
@SuppressWarnings("rawtypes")
public static List arrayToList(Object source) {
return Arrays.asList(ObjectUtils.toObjectArray(source));
}
/**
* Merge the given array into the given Collection.
*
* @param array
* the array to merge (may be {@code 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 = ObjectUtils.toObjectArray(array);
for (Object elem : arr) {
collection.add((E) elem);
}
}
/**
* Merge the given Properties instance into the given Map, copying all
* properties (key-value pairs) over.
*
* Uses {@code Properties.propertyNames()} to even catch default properties
* linked into the original Properties instance.
*
* @param props
* the Properties instance to merge (may be {@code 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((K) key, (V) value);
}
}
}
/**
* Check whether the given Iterator contains the given element.
*
* @param iterator
* the Iterator to check
* @param element
* the element to look for
* @return {@code true} if found, {@code false} else
*/
public static boolean contains(Iterator iterator, Object element) {
if (iterator != null) {
while (iterator.hasNext()) {
Object candidate = iterator.next();
if (ObjectUtils.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 {@code true} if found, {@code false} else
*/
public static boolean contains(Enumeration enumeration, Object element) {
if (enumeration != null) {
while (enumeration.hasMoreElements()) {
Object candidate = enumeration.nextElement();
if (ObjectUtils.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
* {@code true} for an equal element as well.
*
* @param collection
* the Collection to check
* @param element
* the element to look for
* @return {@code true} if found, {@code 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 {@code true} if any element in '{@code candidates}' is contained
* in '{@code source}'; otherwise returns {@code 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 '{@code candidates}' that is contained in '
* {@code source}'. If no element in '{@code candidates}' is present in '
* {@code source}' returns {@code 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 {@code null} if not found
*/
@SuppressWarnings("unchecked")
public static E findFirstMatch(Collection source, Collection candidates) {
if (isEmpty(source) || isEmpty(candidates)) {
return null;
}
for (Object candidate : candidates) {
if (source.contains(candidate)) {
return (E) 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
* @return a value of the given type found if there is a clear match, or
* {@code 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 {@code null} if none or more than one such value found
*/
public static Object findValueOfType(Collection collection, Class[] types) {
if (isEmpty(collection) || ObjectUtils.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 {@code true} if the collection contains a single reference or
* multiple references to the same instance, {@code 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 {@code 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.
*/
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
* @return the iterator
*/
public static Iterator toIterator(Enumeration enumeration) {
return new EnumerationIterator(enumeration);
}
/**
* Iterator wrapping an Enumeration.
*/
private static class EnumerationIterator implements Iterator {
private final Enumeration enumeration;
public EnumerationIterator(Enumeration enumeration) {
this.enumeration = enumeration;
}
@Override
public boolean hasNext() {
return this.enumeration.hasMoreElements();
}
@Override
public E next() {
return this.enumeration.nextElement();
}
@Override
public void remove() throws UnsupportedOperationException {
throw new UnsupportedOperationException("Not supported");
}
}
}