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.IntConsumer; 28 import java.util.function.IntSupplier; 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 int} value. 34 * If a value is present, {@code isPresent()} will return {@code true} and 35 * {@code getAsInt()} 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(int) orElse()} 39 * (return a default value if value not present) and 40 * {@link #ifPresent(java.util.function.IntConsumer) ifPresent()} (execute a block 41 * of code if the value is present). 42 * 43 * @since 1.8 44 */ 45 public final class OptionalInt { 46 /** 47 * Common instance for {@code empty()}. 48 */ 49 private static final OptionalInt EMPTY = new OptionalInt(); 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 int value; 56 57 /** 58 * Construct an empty instance. 59 * 60 * @implNote Generally only one empty instance, {@link OptionalInt#EMPTY}, 61 * should exist per VM. 62 */ OptionalInt()63 private OptionalInt() { 64 this.isPresent = false; 65 this.value = 0; 66 } 67 68 /** 69 * Returns an empty {@code OptionalInt} instance. No value is present for this 70 * OptionalInt. 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 OptionalInt} 78 */ empty()79 public static OptionalInt empty() { 80 return EMPTY; 81 } 82 83 /** 84 * Construct an instance with the value present. 85 * 86 * @param value the int value to be present 87 */ OptionalInt(int value)88 private OptionalInt(int value) { 89 this.isPresent = true; 90 91 this.value = value; 92 } 93 94 /** 95 * Return an {@code OptionalInt} with the specified value present. 96 * 97 * @param value the value to be present 98 * @return an {@code OptionalInt} with the value present 99 */ of(int value)100 public static OptionalInt of(int value) { 101 return new OptionalInt(value); 102 } 103 104 /** 105 * If a value is present in this {@code OptionalInt}, returns the value, 106 * otherwise throws {@code NoSuchElementException}. 107 * 108 * @return the value held by this {@code OptionalInt} 109 * @throws NoSuchElementException if there is no value present 110 * 111 * @see OptionalInt#isPresent() 112 */ getAsInt()113 public int getAsInt() { 114 if (!isPresent) { 115 throw new NoSuchElementException("No value present"); 116 } 117 return value; 118 } 119 120 /** 121 * Return {@code true} if there is a value present, otherwise {@code false}. 122 * 123 * @return {@code true} if there is a value present, otherwise {@code false} 124 */ isPresent()125 public boolean isPresent() { 126 return isPresent; 127 } 128 129 /** 130 * Have the specified consumer accept the value if a value is present, 131 * otherwise do nothing. 132 * 133 * @param consumer block to be executed if a value is present 134 * @throws NullPointerException if value is present and {@code consumer} is 135 * null 136 */ ifPresent(IntConsumer consumer)137 public void ifPresent(IntConsumer consumer) { 138 if (isPresent) 139 consumer.accept(value); 140 } 141 142 /** 143 * Return the value if present, otherwise return {@code other}. 144 * 145 * @param other the value to be returned if there is no value present 146 * @return the value, if present, otherwise {@code other} 147 */ orElse(int other)148 public int orElse(int other) { 149 return isPresent ? value : other; 150 } 151 152 /** 153 * Return the value if present, otherwise invoke {@code other} and return 154 * the result of that invocation. 155 * 156 * @param other a {@code IntSupplier} whose result is returned if no value 157 * is present 158 * @return the value if present otherwise the result of {@code other.getAsInt()} 159 * @throws NullPointerException if value is not present and {@code other} is 160 * null 161 */ orElseGet(IntSupplier other)162 public int orElseGet(IntSupplier other) { 163 return isPresent ? value : other.getAsInt(); 164 } 165 166 /** 167 * Return the contained value, if present, otherwise throw an exception 168 * to be created by the provided supplier. 169 * 170 * @apiNote A method reference to the exception constructor with an empty 171 * argument list can be used as the supplier. For example, 172 * {@code IllegalStateException::new} 173 * 174 * @param <X> Type of the exception to be thrown 175 * @param exceptionSupplier The supplier which will return the exception to 176 * be thrown 177 * @return the present value 178 * @throws X if there is no value present 179 * @throws NullPointerException if no value is present and 180 * {@code exceptionSupplier} is null 181 */ orElseThrow(Supplier<X> exceptionSupplier)182 public<X extends Throwable> int orElseThrow(Supplier<X> exceptionSupplier) throws X { 183 if (isPresent) { 184 return value; 185 } else { 186 throw exceptionSupplier.get(); 187 } 188 } 189 190 /** 191 * Indicates whether some other object is "equal to" this OptionalInt. The 192 * other object is considered equal if: 193 * <ul> 194 * <li>it is also an {@code OptionalInt} and; 195 * <li>both instances have no value present or; 196 * <li>the present values are "equal to" each other via {@code ==}. 197 * </ul> 198 * 199 * @param obj an object to be tested for equality 200 * @return {code true} if the other object is "equal to" this object 201 * otherwise {@code false} 202 */ 203 @Override equals(Object obj)204 public boolean equals(Object obj) { 205 if (this == obj) { 206 return true; 207 } 208 209 if (!(obj instanceof OptionalInt)) { 210 return false; 211 } 212 213 OptionalInt other = (OptionalInt) obj; 214 return (isPresent && other.isPresent) 215 ? value == other.value 216 : isPresent == other.isPresent; 217 } 218 219 /** 220 * Returns the hash code value of the present value, if any, or 0 (zero) if 221 * no value is present. 222 * 223 * @return hash code value of the present value or 0 if no value is present 224 */ 225 @Override hashCode()226 public int hashCode() { 227 return isPresent ? Integer.hashCode(value) : 0; 228 } 229 230 /** 231 * {@inheritDoc} 232 * 233 * Returns a non-empty string representation of this object suitable for 234 * debugging. The exact presentation format is unspecified and may vary 235 * between implementations and versions. 236 * 237 * @implSpec If a value is present the result must include its string 238 * representation in the result. Empty and present instances must be 239 * unambiguously differentiable. 240 * 241 * @return the string representation of this instance 242 */ 243 @Override toString()244 public String toString() { 245 return isPresent 246 ? String.format("OptionalInt[%s]", value) 247 : "OptionalInt.empty"; 248 } 249 } 250