1 /* 2 * Copyright (C) 2007 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 5 * in compliance with the License. You may obtain a copy of the License at 6 * 7 * http://www.apache.org/licenses/LICENSE-2.0 8 * 9 * Unless required by applicable law or agreed to in writing, software distributed under the License 10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 11 * or implied. See the License for the specific language governing permissions and limitations under 12 * the License. 13 */ 14 15 package com.google.common.base; 16 17 import static com.google.common.base.Preconditions.checkNotNull; 18 19 import com.google.common.annotations.GwtIncompatible; 20 import javax.annotation.CheckForNull; 21 22 /** 23 * This class provides default values for all Java types, as defined by the JLS. 24 * 25 * @author Ben Yu 26 * @since 1.0 27 */ 28 @GwtIncompatible 29 @ElementTypesAreNonnullByDefault 30 public final class Defaults { Defaults()31 private Defaults() {} 32 33 private static final Double DOUBLE_DEFAULT = 0d; 34 private static final Float FLOAT_DEFAULT = 0f; 35 36 /** 37 * Returns the default value of {@code type} as defined by JLS --- {@code 0} for numbers, {@code 38 * false} for {@code boolean} and {@code '\0'} for {@code char}. For non-primitive types and 39 * {@code void}, {@code null} is returned. 40 */ 41 @SuppressWarnings("unchecked") 42 @CheckForNull defaultValue(Class<T> type)43 public static <T> T defaultValue(Class<T> type) { 44 checkNotNull(type); 45 if (type.isPrimitive()) { 46 if (type == boolean.class) { 47 return (T) Boolean.FALSE; 48 } else if (type == char.class) { 49 return (T) Character.valueOf('\0'); 50 } else if (type == byte.class) { 51 return (T) Byte.valueOf((byte) 0); 52 } else if (type == short.class) { 53 return (T) Short.valueOf((short) 0); 54 } else if (type == int.class) { 55 return (T) Integer.valueOf(0); 56 } else if (type == long.class) { 57 return (T) Long.valueOf(0L); 58 } else if (type == float.class) { 59 return (T) FLOAT_DEFAULT; 60 } else if (type == double.class) { 61 return (T) DOUBLE_DEFAULT; 62 } 63 } 64 return null; 65 } 66 } 67