UnmodifiableCollectionUtil.java
///////////////////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
// Copyright (C) 2001-2024 the original author or authors.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
///////////////////////////////////////////////////////////////////////////////////////////////
package com.puppycrawl.tools.checkstyle.utils;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;
/**
* <p>Note: it simply wraps the existing JDK methods to provide a workaround
* for Pitest survival on mutation for removal of immutable wrapping,
* see #13127 for more details.
* </p>
*
*/
public final class UnmodifiableCollectionUtil {
/**
* Private constructor for UnmodifiableCollectionUtil.
*
*/
private UnmodifiableCollectionUtil() {
}
/**
* Creates an unmodifiable list based on the provided collection.
*
* @param collection the collection to create an unmodifiable list from
* @param <T> the type of elements in the set
* @return an unmodifiable list containing the elements from the provided collection
*/
public static <T> List<T> unmodifiableList(List<T> collection) {
return Collections.unmodifiableList(collection);
}
/**
* Returns an unmodifiable view of a List containing elements of a specific type.
*
* @param items The List of items to make unmodifiable.
* @param elementType The Class object representing the type of elements in the list.
* @param <S> The generic type of elements in the input Collection.
* @param <T> The type of elements in the resulting unmodifiable List.
* @return An unmodifiable List containing elements of the specified type.
*/
public static <S, T> List<T> unmodifiableList(Collection<S> items, Class<T> elementType) {
return items.stream()
.map(elementType::cast)
.collect(Collectors.toUnmodifiableList());
}
/**
* Creates a copy of array.
*
* @param array Array to create a copy of
* @param length length of array
* @param <T> The type of array
* @return copy of array
*/
public static <T> T[] copyOfArray(T[] array, int length) {
return Arrays.copyOf(array, length);
}
/**
* Creates a copy of Map.
*
* @param map map to create a copy of
* @param <K> the type of keys in the map
* @param <V> the type of values in the map
* @return an immutable copy of the input map
*/
public static <K, V> Map<K, V> copyOfMap(Map<? extends K, ? extends V> map) {
return Map.copyOf(map);
}
/**
* Returns an immutable set containing only the specified object.
*
* @param obj the type of object in the set
* @param <T> the type of object
* @return immutable set
*/
public static <T> Set<T> singleton(T obj) {
return Collections.singleton(obj);
}
}