001/* 002 * Copyright (C) 2007 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 005 * in compliance with the License. You may obtain a copy of the License at 006 * 007 * http://www.apache.org/licenses/LICENSE-2.0 008 * 009 * Unless required by applicable law or agreed to in writing, software distributed under the License 010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 011 * or implied. See the License for the specific language governing permissions and limitations under 012 * the License. 013 */ 014 015package com.google.common.base; 016 017import static com.google.common.base.Preconditions.checkNotNull; 018 019import com.google.common.annotations.GwtIncompatible; 020import com.google.common.annotations.J2ktIncompatible; 021import javax.annotation.CheckForNull; 022 023/** 024 * This class provides default values for all Java types, as defined by the JLS. 025 * 026 * @author Ben Yu 027 * @since 1.0 028 */ 029@J2ktIncompatible 030@GwtIncompatible 031@ElementTypesAreNonnullByDefault 032public final class Defaults { 033 private Defaults() {} 034 035 private static final Double DOUBLE_DEFAULT = 0d; 036 private static final Float FLOAT_DEFAULT = 0f; 037 038 /** 039 * Returns the default value of {@code type} as defined by JLS --- {@code 0} for numbers, {@code 040 * false} for {@code boolean} and {@code '\0'} for {@code char}. For non-primitive types and 041 * {@code void}, {@code null} is returned. 042 */ 043 @SuppressWarnings("unchecked") 044 @CheckForNull 045 public static <T> T defaultValue(Class<T> type) { 046 checkNotNull(type); 047 if (type.isPrimitive()) { 048 if (type == boolean.class) { 049 return (T) Boolean.FALSE; 050 } else if (type == char.class) { 051 return (T) Character.valueOf('\0'); 052 } else if (type == byte.class) { 053 return (T) Byte.valueOf((byte) 0); 054 } else if (type == short.class) { 055 return (T) Short.valueOf((short) 0); 056 } else if (type == int.class) { 057 return (T) Integer.valueOf(0); 058 } else if (type == long.class) { 059 return (T) Long.valueOf(0L); 060 } else if (type == float.class) { 061 return (T) FLOAT_DEFAULT; 062 } else if (type == double.class) { 063 return (T) DOUBLE_DEFAULT; 064 } 065 } 066 return null; 067 } 068}