1 /* 2 * Copyright (C) 2011 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.base; 18 19 import static com.google.common.base.Preconditions.checkNotNull; 20 21 import com.google.common.annotations.GwtCompatible; 22 23 import java.util.Collections; 24 import java.util.Set; 25 26 import javax.annotation.Nullable; 27 28 /** 29 * Implementation of an {@link Optional} containing a reference. 30 */ 31 @GwtCompatible 32 final class Present<T> extends Optional<T> { 33 private final T reference; 34 Present(T reference)35 Present(T reference) { 36 this.reference = reference; 37 } 38 isPresent()39 @Override public boolean isPresent() { 40 return true; 41 } 42 get()43 @Override public T get() { 44 return reference; 45 } 46 or(T defaultValue)47 @Override public T or(T defaultValue) { 48 checkNotNull(defaultValue, "use Optional.orNull() instead of Optional.or(null)"); 49 return reference; 50 } 51 or(Optional<? extends T> secondChoice)52 @Override public Optional<T> or(Optional<? extends T> secondChoice) { 53 checkNotNull(secondChoice); 54 return this; 55 } 56 or(Supplier<? extends T> supplier)57 @Override public T or(Supplier<? extends T> supplier) { 58 checkNotNull(supplier); 59 return reference; 60 } 61 orNull()62 @Override public T orNull() { 63 return reference; 64 } 65 asSet()66 @Override public Set<T> asSet() { 67 return Collections.singleton(reference); 68 } 69 transform(Function<? super T, V> function)70 @Override public <V> Optional<V> transform(Function<? super T, V> function) { 71 return new Present<V>(checkNotNull(function.apply(reference), 72 "the Function passed to Optional.transform() must not return null.")); 73 } 74 equals(@ullable Object object)75 @Override public boolean equals(@Nullable Object object) { 76 if (object instanceof Present) { 77 Present<?> other = (Present<?>) object; 78 return reference.equals(other.reference); 79 } 80 return false; 81 } 82 hashCode()83 @Override public int hashCode() { 84 return 0x598df91c + reference.hashCode(); 85 } 86 toString()87 @Override public String toString() { 88 return "Optional.of(" + reference + ")"; 89 } 90 91 private static final long serialVersionUID = 0; 92 } 93