com.fizzed.crux.util.MaybeStream Maven / Gradle / Ivy
/*
* Copyright 2018 Fizzed, Inc.
*
* 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 com.fizzed.crux.util;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.function.BiConsumer;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
/**
* A null-safe way of working with iterables and arrays as streams. Useful
* for iterating with indexes too :-)
*
* @author jjlauer
* @param The type of Maybe
*/
public class MaybeStream implements Iterable {
final private Iterable values;
protected MaybeStream(Iterable values) {
this.values = values;
}
public Stream get() {
if (values == null) {
throw new NoSuchElementException("No values present");
}
return this.stream();
}
public Stream stream() {
if (values == null) {
return Stream.empty();
}
// optimized for collections (e.g. List)
if (values instanceof Collection) {
return ((Collection)values).stream();
} else {
return StreamSupport.stream(this.values.spliterator(), false);
}
}
@Override
public Iterator iterator() {
if (values == null) {
return new ArrayIterator<>(null); // empty
}
// optimized for collections (e.g. List)
if (values instanceof Collection) {
return ((Collection)values).iterator();
} else {
return values.iterator();
}
}
public MaybeStream forEach(BiConsumer consumer) {
if (values == null) {
return this;
}
IterableIter iter = new IterableIter<>(this.values);
iter.forEach(consumer);
return this;
}
public boolean isPresent() {
return this.values != null;
}
public boolean isAbsent() {
return this.values == null;
}
static public MaybeStream empty() {
return new MaybeStream<>(null);
}
static public MaybeStream of(T[] values) {
if (values == null) {
return empty();
}
return maybeStream(new ArrayIterable<>(values));
}
static public MaybeStream of(Iterable values) {
return maybeStream(values);
}
static public MaybeStream maybeStream(T[] values) {
return MaybeStream.of(values);
}
static public MaybeStream maybeStream(Iterable value) {
return new MaybeStream<>(value);
}
// helpers
static public class ArrayIterable implements Iterable {
private final V[] values;
public ArrayIterable(V[] values) {
this.values = values;
}
@Override
public Iterator iterator() {
return new ArrayIterator<>(this.values);
}
}
static public class ArrayIterator implements Iterator {
private final V[] values;
private int index;
public ArrayIterator(V[] values) {
this.values = values;
this.index = 0;
}
@Override
public boolean hasNext() {
return this.values != null && this.index < this.values.length;
}
@Override
public V next() {
V value = this.values[this.index];
this.index++;
return value;
}
}
static public interface Iter {
void forEach(BiConsumer consumer);
}
static public class IterableIter implements Iter {
private final Iterable values;
public IterableIter(Iterable values) {
this.values = values;
}
@Override
public void forEach(BiConsumer consumer) {
if (this.values == null) {
return;
}
final Iterator iterator = this.values.iterator();
int i = 0;
while (iterator.hasNext()) {
V value = iterator.next();
consumer.accept(value, i);
i++;
}
}
}
}