JarCastingCollectionHelper
What is it?
A set of static utility methods to simplify filtering and querying Java's Collections.
A limited subset of .NET framework's LINQ Enumerable Methods for Java.
Methods
Filter
Filters a collection using the given predicate
List<T> filter(Collection<T> items, Predicate<T> predicate)
First
Returns the first element from a collection that matches the given predicate. Throws an exception if no matching element is found
T first(Collection<T> items, Predicate<T> predicate)
First or null
Returns the first element from a collection that matches the given predicate or null if no matching element is found
T firstOrNull(Collection<T> items, Predicate<T> predicate)
Any
Returns true if any element of a collection matches the given predicate
boolean any(Collection<T> items, Predicate<T> predicate)
All
Returns true if all elements of a collection match the given predicate
boolean all(Collection<T> items, Predicate<T> predicate)
Is empty
Returns true if the collection is null or contains no elements
boolean isEmpty(Collection items)
Single
Returns the only element from a collection that matches the given predicate. Throws an exception if the number of found elements is not exactly 1
T single(Collection<T> items, Predicate<T> predicate)
Single or null
Returns the only element from a collection that matches the given predicate or null if such element is not found. Throws an exception if there is more than 1 element matching the predicate
T singleOrNull(Collection<T> items, Predicate<T> predicate)
Count
Returns the number of elements in a collection matching the given predicate
int count(Collection<T> items, Predicate<T> predicate)
Map
Projects each element of a collection into a new collection
List<TResult> map(Collection<TSource> items, Mapper<TSource, TResult> mapper)
Javadoc
Usage
Add using Gradle:
compile 'com.github.simonpercic:collectionhelper:1.2.1'
Use
// sample list
List<Integer> integerList = Arrays.asList(1, 4, 2, 7, 8, 0, 5);
// filter
List<Integer> largerThan2 = CollectionHelper.filter(integerList, new Predicate<Integer>() {
@Override public boolean apply(Integer intValue) {
return intValue > 2;
}
});
// map
List<String> mappedList = CollectionHelper.map(integerList, new Mapper<Integer, String>() {
@Override public String map(Integer intValue) {
return String.format("myString_%d", intValue);
}
});
Android Pro-tip
Use the awesome Gradle Retrolambda Plugin with Java 8 to use lambdas:
// filter
List<Integer> largerThan2 = CollectionHelper.filter(integerList, intValue -> intValue > 2);
// map
List<String> mappedList = CollectionHelper.map(integerList, intValue -> String.format("myString_%d", intValue));
// or even using a method reference
List<String> simpleMappedList = CollectionHelper.map(integerList, String::valueOf);
Appendix
If you are using Java 8 and are NOT on Android you can also use Streams to simplify working with Collections.
Change Log
See CHANGELOG.md
License
Open source, distributed under the MIT License. See LICENSE for details.