1 /* 2 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 package java.util; 26 27 import java.util.function.LongConsumer; 28 import java.util.function.LongSupplier; 29 import java.util.function.Supplier; 30 31 // Android-changed: removed ValueBased paragraph. 32 /** 33 * A container object which may or may not contain a {@code long} value. 34 * If a value is present, {@code isPresent()} will return {@code true} and 35 * {@code getAsLong()} will return the value. 36 * 37 * <p>Additional methods that depend on the presence or absence of a contained 38 * value are provided, such as {@link #orElse(long) orElse()} 39 * (return a default value if value not present) and 40 * {@link #ifPresent(java.util.function.LongConsumer) ifPresent()} (execute a block 41 * of code if the value is present). 42 * 43 * @since 1.8 44 */ 45 public final class OptionalLong { 46 /** 47 * Common instance for {@code empty()}. 48 */ 49 private static final OptionalLong EMPTY = new OptionalLong(); 50 51 /** 52 * If true then the value is present, otherwise indicates no value is present 53 */ 54 private final boolean isPresent; 55 private final long value; 56 57 /** 58 * Construct an empty instance. 59 * 60 * @implNote generally only one empty instance, {@link OptionalLong#EMPTY}, 61 * should exist per VM. 62 */ 63 private OptionalLong() { 64 this.isPresent = false; 65 this.value = 0; 66 } 67 68 /** 69 * Returns an empty {@code OptionalLong} instance. No value is present for this 70 * OptionalLong. 71 * 72 * @apiNote Though it may be tempting to do so, avoid testing if an object 73 * is empty by comparing with {@code ==} against instances returned by 74 * {@code Option.empty()}. There is no guarantee that it is a singleton. 75 * Instead, use {@link #isPresent()}. 76 * 77 * @return an empty {@code OptionalLong}. 78 */ 79 public static OptionalLong empty() { 80 return EMPTY; 81 } 82 83 /** 84 * Construct an instance with the value present. 85 * 86 * @param value the long value to be present 87 */ 88 private OptionalLong(long value) { 89 this.isPresent = true; 90 this.value = value; 91 } 92 93 /** 94 * Return an {@code OptionalLong} with the specified value present. 95 * 96 * @param value the value to be present 97 * @return an {@code OptionalLong} with the value present 98 */ 99 public static OptionalLong of(long value) { 100 return new OptionalLong(value); 101 } 102 103 /** 104 * If a value is present in this {@code OptionalLong}, returns the value, 105 * otherwise throws {@code NoSuchElementException}. 106 * 107 * @return the value held by this {@code OptionalLong} 108 * @throws NoSuchElementException if there is no value present 109 * 110 * @see OptionalLong#isPresent() 111 */ 112 public long getAsLong() { 113 if (!isPresent) { 114 throw new NoSuchElementException("No value present"); 115 } 116 return value; 117 } 118 119 /** 120 * Return {@code true} if there is a value present, otherwise {@code false}. 121 * 122 * @return {@code true} if there is a value present, otherwise {@code false} 123 */ 124 public boolean isPresent() { 125 return isPresent; 126 } 127 128 /** 129 * Have the specified consumer accept the value if a value is present, 130 * otherwise do nothing. 131 * 132 * @param consumer block to be executed if a value is present 133 * @throws NullPointerException if value is present and {@code consumer} is 134 * null 135 */ 136 public void ifPresent(LongConsumer consumer) { 137 if (isPresent) 138 consumer.accept(value); 139 } 140 141 /** 142 * Return the value if present, otherwise return {@code other}. 143 * 144 * @param other the value to be returned if there is no value present 145 * @return the value, if present, otherwise {@code other} 146 */ 147 public long orElse(long other) { 148 return isPresent ? value : other; 149 } 150 151 /** 152 * Return the value if present, otherwise invoke {@code other} and return 153 * the result of that invocation. 154 * 155 * @param other a {@code LongSupplier} whose result is returned if no value 156 * is present 157 * @return the value if present otherwise the result of {@code other.getAsLong()} 158 * @throws NullPointerException if value is not present and {@code other} is 159 * null 160 */ 161 public long orElseGet(LongSupplier other) { 162 return isPresent ? value : other.getAsLong(); 163 } 164 165 /** 166 * Return the contained value, if present, otherwise throw an exception 167 * to be created by the provided supplier. 168 * 169 * @apiNote A method reference to the exception constructor with an empty 170 * argument list can be used as the supplier. For example, 171 * {@code IllegalStateException::new} 172 * 173 * @param <X> Type of the exception to be thrown 174 * @param exceptionSupplier The supplier which will return the exception to 175 * be thrown 176 * @return the present value 177 * @throws X if there is no value present 178 * @throws NullPointerException if no value is present and 179 * {@code exceptionSupplier} is null 180 */ 181 public<X extends Throwable> long orElseThrow(Supplier<X> exceptionSupplier) throws X { 182 if (isPresent) { 183 return value; 184 } else { 185 throw exceptionSupplier.get(); 186 } 187 } 188 189 /** 190 * Indicates whether some other object is "equal to" this OptionalLong. The 191 * other object is considered equal if: 192 * <ul> 193 * <li>it is also an {@code OptionalLong} and; 194 * <li>both instances have no value present or; 195 * <li>the present values are "equal to" each other via {@code ==}. 196 * </ul> 197 * 198 * @param obj an object to be tested for equality 199 * @return {code true} if the other object is "equal to" this object 200 * otherwise {@code false} 201 */ 202 @Override 203 public boolean equals(Object obj) { 204 if (this == obj) { 205 return true; 206 } 207 208 if (!(obj instanceof OptionalLong)) { 209 return false; 210 } 211 212 OptionalLong other = (OptionalLong) obj; 213 return (isPresent && other.isPresent) 214 ? value == other.value 215 : isPresent == other.isPresent; 216 } 217 218 /** 219 * Returns the hash code value of the present value, if any, or 0 (zero) if 220 * no value is present. 221 * 222 * @return hash code value of the present value or 0 if no value is present 223 */ 224 @Override 225 public int hashCode() { 226 return isPresent ? Long.hashCode(value) : 0; 227 } 228 229 /** 230 * {@inheritDoc} 231 * 232 * Returns a non-empty string representation of this object suitable for 233 * debugging. The exact presentation format is unspecified and may vary 234 * between implementations and versions. 235 * 236 * @implSpec If a value is present the result must include its string 237 * representation in the result. Empty and present instances must be 238 * unambiguously differentiable. 239 * 240 * @return the string representation of this instance 241 */ 242 @Override 243 public String toString() { 244 return isPresent 245 ? String.format("OptionalLong[%s]", value) 246 : "OptionalLong.empty"; 247 } 248 } 249
