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8050820: Please add java.util.Optional.stream() to convert Optional<T> to Stream<T>

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Reviewed-by: alundblad, forax, chegar, jrose
This commit is contained in:
Paul Sandoz 2015-02-02 14:19:12 +01:00
parent 3b9021981f
commit dd21d2c4db
8 changed files with 225 additions and 42 deletions
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42
jdk/src/java.base/share/classes/java/util/Optional.java
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2012, 2015, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@ -28,6 +28,7 @@ import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.Supplier;
import java.util.stream.Stream;
/**
* A container object which may or may not contain a non-null value.
@ -155,8 +156,9 @@ public final class Optional<T> {
* null
*/
public void ifPresent(Consumer<? super T> consumer) {
if (value != null)
if (value != null) {
consumer.accept(value);
}
}
/**
@ -172,10 +174,11 @@ public final class Optional<T> {
*/
public Optional<T> filter(Predicate<? super T> predicate) {
Objects.requireNonNull(predicate);
if (!isPresent())
if (!isPresent()) {
return this;
else
} else {
return predicate.test(value) ? this : empty();
}
}
/**
@ -209,9 +212,9 @@ public final class Optional<T> {
*/
public<U> Optional<U> map(Function<? super T, ? extends U> mapper) {
Objects.requireNonNull(mapper);
if (!isPresent())
if (!isPresent()) {
return empty();
else {
} else {
return Optional.ofNullable(mapper.apply(value));
}
}
@ -235,13 +238,36 @@ public final class Optional<T> {
*/
public<U> Optional<U> flatMap(Function<? super T, Optional<U>> mapper) {
Objects.requireNonNull(mapper);
if (!isPresent())
if (!isPresent()) {
return empty();
else {
} else {
return Objects.requireNonNull(mapper.apply(value));
}
}
/**
* If a value is present return a sequential {@link Stream} containing only
* that value, otherwise return an empty {@code Stream}.
*
* @apiNote This method can be used to transform a {@code Stream} of
* optional elements to a {@code Stream} of present value elements:
*
* <pre>{@code
* Stream<Optional<T>> os = ..
* Stream<T> s = os.flatMap(Optional::stream)
* }</pre>
*
* @return the optional value as a {@code Stream}
* @since 1.9
*/
public Stream<T> stream() {
if (!isPresent()) {
return Stream.empty();
} else {
return Stream.of(value);
}
}
/**
* Return the value if present, otherwise return {@code other}.
*