jdk/src/java.base/share/classes/java/util/OptionalInt.java - platform/libcore - Git at Google

 /*
  * 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
  * 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(java.util.function.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.
  *
  * @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}.
      *
      * @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";
     }
 }
	/*
	* 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
	* 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(java.util.function.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.
	*
	* @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}.
	*
	* @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";
	}
	}