org.springframework.data.gemfire.util.CollectionUtils Maven / Gradle / Ivy
/*
* Copyright 2010-2013 the original author or authors.
*
* 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 org.springframework.data.gemfire.util;
import java.util.Collection;
import java.util.Collections;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* The CollectionUtils class is a utility class for working with Java Collections Framework and classes.
*
* @author John Blum
* @see java.util.Collection
* @see java.util.Collections
* @see org.springframework.util.CollectionUtils
* @since 1.7.0
*/
@SuppressWarnings("unused")
public abstract class CollectionUtils extends org.springframework.util.CollectionUtils {
/**
* Adapts the given Enumeration as an Iterable object for use within a for each loop.
*
* @param the class type of the Enumeration elements.
* @param enumeration the Enumeration to adapt as an Iterable object.
* @return an Iterable instance of the Enumeration.
* @see java.lang.Iterable
* @see java.util.Enumeration
*/
public static Iterable iterable(final Enumeration enumeration) {
return new Iterable() {
@Override public Iterator iterator() {
return org.springframework.util.CollectionUtils.toIterator(enumeration);
}
};
}
/**
* Adapts the given Iterator as an Iterable object for use within a for each loop.
*
* @param the class type of the Iterator elements.
* @param iterator the Iterator to adapt as an Iterable object.
* @return an Iterable instance of the Iterator.
* @see java.lang.Iterable
* @see java.util.Iterator
*/
public static Iterable iterable(final Iterator iterator) {
return new Iterable() {
@Override public Iterator iterator() {
return iterator;
}
};
}
/**
* A null-safe operation returning the original Collection if non-null or an empty Collection
* (implemented with List) if null.
*
* @param the element class type of the Collection.
* @param collection the Collection to evaluate for being null.
* @return the given Collection if not null, otherwise return an empty Collection (List).
* @see java.util.Collections#emptyList()
*/
public static Collection nullSafeCollection(final Collection collection) {
return (collection != null ? collection : Collections.emptyList());
}
/**
* A null-safe operation returning the original Iterable object if non-null or a default, empty Iterable
* implementation if null.
*
* @param the class type of the iterable elements.
* @param iterable the Iterable object evaluated for a null reference.
* @return the Iterable object if not null or a default, empty Iterable implementation otherwise.
* @see java.lang.Iterable
* @see java.util.Iterator
*/
public static Iterable nullSafeIterable(Iterable iterable) {
return (iterable != null ? iterable : new Iterable() {
@Override public Iterator iterator() {
return new Iterator() {
@Override public boolean hasNext() {
return false;
}
@Override public T next() {
throw new NoSuchElementException("no elements in this Iterator");
}
@Override public void remove() {
throw new UnsupportedOperationException("operation not supported");
}
};
}
});
}
}