8187443: Forest Consolidation: Move files to unified layout

Reviewed-by: darcy, ihse

src/java.base/share/classes/java/util/OptionalInt.java

@@ -0,0 +1,311 @@
+/*
+ * Copyright (c) 2012, 2017, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code 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 General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package java.util;
+
+import java.util.function.IntConsumer;
+import java.util.function.IntSupplier;
+import java.util.function.Supplier;
+import java.util.stream.IntStream;
+
+/**
+ * A container object which may or may not contain an {@code int} value.  If a
+ * value is present, {@code isPresent()} returns {@code true} and
+ * {@code getAsInt()} returns the value.
+ *
+ * <p>Additional methods that depend on the presence or absence of a contained
+ * value are provided, such as {@link #orElse(int) orElse()}
+ * (returns a default value if no value is present) and
+ * {@link #ifPresent(IntConsumer) ifPresent()} (performs an
+ * action if a value is present).
+ *
+ * <p>This is a <a href="../lang/doc-files/ValueBased.html">value-based</a>
+ * class; use of identity-sensitive operations (including reference equality
+ * ({@code ==}), identity hash code, or synchronization) on instances of
+ * {@code OptionalInt} may have unpredictable results and should be avoided.
+ *
+ * @apiNote
+ * {@code OptionalInt} is primarily intended for use as a method return type where
+ * there is a clear need to represent "no result." A variable whose type is
+ * {@code OptionalInt} should never itself be {@code null}; it should always point
+ * to an {@code OptionalInt} instance.
+ *
+ * @since 1.8
+ */
+public final class OptionalInt {
+    /**
+     * Common instance for {@code empty()}.
+     */
+    private static final OptionalInt EMPTY = new OptionalInt();
+
+    /**
+     * If true then the value is present, otherwise indicates no value is present
+     */
+    private final boolean isPresent;
+    private final int value;
+
+    /**
+     * Construct an empty instance.
+     *
+     * @implNote Generally only one empty instance, {@link OptionalInt#EMPTY},
+     * should exist per VM.
+     */
+    private OptionalInt() {
+        this.isPresent = false;
+        this.value = 0;
+    }
+
+    /**
+     * Returns an empty {@code OptionalInt} instance.  No value is present for
+     * this {@code OptionalInt}.
+     *
+     * @apiNote
+     * Though it may be tempting to do so, avoid testing if an object is empty
+     * by comparing with {@code ==} against instances returned by
+     * {@code OptionalInt.empty()}.  There is no guarantee that it is a singleton.
+     * Instead, use {@link #isPresent()}.
+     *
+     * @return an empty {@code OptionalInt}
+     */
+    public static OptionalInt empty() {
+        return EMPTY;
+    }
+
+    /**
+     * Construct an instance with the described value.
+     *
+     * @param value the int value to describe
+     */
+    private OptionalInt(int value) {
+        this.isPresent = true;
+        this.value = value;
+    }
+
+    /**
+     * Returns an {@code OptionalInt} describing the given value.
+     *
+     * @param value the value to describe
+     * @return an {@code OptionalInt} with the value present
+     */
+    public static OptionalInt of(int value) {
+        return new OptionalInt(value);
+    }
+
+    /**
+     * If a value is present, returns the value, otherwise throws
+     * {@code NoSuchElementException}.
+     *
+     * @apiNote
+     * The methods {@link #orElse(int) orElse} and
+     * {@link #orElseGet(IntSupplier) orElseGet}
+     * are generally preferable to this method, as they return a substitute
+     * value if the value is absent, instead of throwing an exception.
+     *
+     * @return the value described by this {@code OptionalInt}
+     * @throws NoSuchElementException if no value is present
+     * @see OptionalInt#isPresent()
+     */
+    public int getAsInt() {
+        if (!isPresent) {
+            throw new NoSuchElementException("No value present");
+        }
+        return value;
+    }
+
+    /**
+     * If a value is present, returns {@code true}, otherwise {@code false}.
+     *
+     * @return {@code true} if a value is present, otherwise {@code false}
+     */
+    public boolean isPresent() {
+        return isPresent;
+    }
+
+    /**
+     * If a value is present, performs the given action with the value,
+     * otherwise does nothing.
+     *
+     * @param action the action to be performed, if a value is present
+     * @throws NullPointerException if value is present and the given action is
+     *         {@code null}
+     */
+    public void ifPresent(IntConsumer action) {
+        if (isPresent) {
+            action.accept(value);
+        }
+    }
+
+    /**
+     * If a value is present, performs the given action with the value,
+     * otherwise performs the given empty-based action.
+     *
+     * @param action the action to be performed, if a value is present
+     * @param emptyAction the empty-based action to be performed, if no value is
+     *        present
+     * @throws NullPointerException if a value is present and the given action
+     *         is {@code null}, or no value is present and the given empty-based
+     *         action is {@code null}.
+     * @since 9
+     */
+    public void ifPresentOrElse(IntConsumer action, Runnable emptyAction) {
+        if (isPresent) {
+            action.accept(value);
+        } else {
+            emptyAction.run();
+        }
+    }
+
+    /**
+     * If a value is present, returns a sequential {@link IntStream} containing
+     * only that value, otherwise returns an empty {@code IntStream}.
+     *
+     * @apiNote
+     * This method can be used to transform a {@code Stream} of optional
+     * integers to an {@code IntStream} of present integers:
+     * <pre>{@code
+     *     Stream<OptionalInt> os = ..
+     *     IntStream s = os.flatMapToInt(OptionalInt::stream)
+     * }</pre>
+     *
+     * @return the optional value as an {@code IntStream}
+     * @since 9
+     */
+    public IntStream stream() {
+        if (isPresent) {
+            return IntStream.of(value);
+        } else {
+            return IntStream.empty();
+        }
+    }
+
+    /**
+     * If a value is present, returns the value, otherwise returns
+     * {@code other}.
+     *
+     * @param other the value to be returned, if no value is present
+     * @return the value, if present, otherwise {@code other}
+     */
+    public int orElse(int other) {
+        return isPresent ? value : other;
+    }
+
+    /**
+     * If a value is present, returns the value, otherwise returns the result
+     * produced by the supplying function.
+     *
+     * @param supplier the supplying function that produces a value to be returned
+     * @return the value, if present, otherwise the result produced by the
+     *         supplying function
+     * @throws NullPointerException if no value is present and the supplying
+     *         function is {@code null}
+     */
+    public int orElseGet(IntSupplier supplier) {
+        return isPresent ? value : supplier.getAsInt();
+    }
+
+    /**
+     * If a value is present, returns the value, otherwise throws an exception
+     * produced by the exception supplying function.
+     *
+     * @apiNote
+     * A method reference to the exception constructor with an empty argument
+     * list can be used as the supplier. For example,
+     * {@code IllegalStateException::new}
+     *
+     * @param <X> Type of the exception to be thrown
+     * @param exceptionSupplier the supplying function that produces an
+     *        exception to be thrown
+     * @return the value, if present
+     * @throws X if no value is present
+     * @throws NullPointerException if no value is present and the exception
+     *         supplying function is {@code null}
+     */
+    public<X extends Throwable> int orElseThrow(Supplier<? extends X> exceptionSupplier) throws X {
+        if (isPresent) {
+            return value;
+        } else {
+            throw exceptionSupplier.get();
+        }
+    }
+
+    /**
+     * Indicates whether some other object is "equal to" this
+     * {@code OptionalInt}.  The other object is considered equal if:
+     * <ul>
+     * <li>it is also an {@code OptionalInt} and;
+     * <li>both instances have no value present or;
+     * <li>the present values are "equal to" each other via {@code ==}.
+     * </ul>
+     *
+     * @param obj an object to be tested for equality
+     * @return {@code true} if the other object is "equal to" this object
+     *         otherwise {@code false}
+     */
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+
+        if (!(obj instanceof OptionalInt)) {
+            return false;
+        }
+
+        OptionalInt other = (OptionalInt) obj;
+        return (isPresent && other.isPresent)
+                ? value == other.value
+                : isPresent == other.isPresent;
+    }
+
+    /**
+     * Returns the hash code of the value, if present, otherwise {@code 0}
+     * (zero) if no value is present.
+     *
+     * @return hash code value of the present value or {@code 0} if no value is
+     *         present
+     */
+    @Override
+    public int hashCode() {
+        return isPresent ? Integer.hashCode(value) : 0;
+    }
+
+    /**
+     * Returns a non-empty string representation of this {@code OptionalInt}
+     * suitable for debugging.  The exact presentation format is unspecified and
+     * may vary between implementations and versions.
+     *
+     * @implSpec
+     * If a value is present the result must include its string representation
+     * in the result.  Empty and present {@code OptionalInt}s must be
+     * unambiguously differentiable.
+     *
+     * @return the string representation of this instance
+     */
+    @Override
+    public String toString() {
+        return isPresent
+                ? String.format("OptionalInt[%s]", value)
+                : "OptionalInt.empty";
+    }
+}