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.Beta; 22 import com.google.common.annotations.GwtCompatible; 23 24 import java.io.Serializable; 25 26 import javax.annotation.Nullable; 27 28 /** 29 * Utility methods for working with {@link Enum} instances. 30 * 31 * @author Steve McKay 32 * 33 * @since 9.0 34 */ 35 @GwtCompatible 36 @Beta 37 public final class Enums { 38 39 private Enums() {} 40 41 /** 42 * Returns a {@link Function} that maps an {@link Enum} name to the associated 43 * {@code Enum} constant. The {@code Function} will return {@code null} if the 44 * {@code Enum} constant does not exist. 45 * 46 * @param enumClass the {@link Class} of the {@code Enum} declaring the 47 * constant values. 48 */ 49 public static <T extends Enum<T>> Function<String, T> valueOfFunction(Class<T> enumClass) { 50 return new ValueOfFunction<T>(enumClass); 51 } 52 53 /** 54 * {@link Function} that maps an {@link Enum} name to the associated 55 * constant, or {@code null} if the constant does not exist. 56 */ 57 private static final class ValueOfFunction<T extends Enum<T>> implements 58 Function<String, T>, Serializable { 59 60 private final Class<T> enumClass; 61 62 private ValueOfFunction(Class<T> enumClass) { 63 this.enumClass = checkNotNull(enumClass); 64 } 65 66 @Override 67 public T apply(String value) { 68 try { 69 return Enum.valueOf(enumClass, value); 70 } catch (IllegalArgumentException e) { 71 return null; 72 } 73 } 74 75 @Override public boolean equals(@Nullable Object obj) { 76 return obj instanceof ValueOfFunction && 77 enumClass.equals(((ValueOfFunction) obj).enumClass); 78 } 79 80 @Override public int hashCode() { 81 return enumClass.hashCode(); 82 } 83 84 @Override public String toString() { 85 return "Enums.valueOf(" + enumClass + ")"; 86 } 87 88 private static final long serialVersionUID = 0; 89 } 90 } 91
