Update #0 - First Release

sources/main/java/com/google/common/base/Defaults.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2007 The Guava Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.common.base;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * This class provides default values for all Java types, as defined by the JLS.
+ *
+ * @author Ben Yu
+ * @since 1.0
+ */
+public final class Defaults {
+	private Defaults() {
+	}
+
+	private static final Map<Class<?>, Object> DEFAULTS;
+
+	static {
+		// Only add to this map via put(Map, Class<T>, T)
+		Map<Class<?>, Object> map = new HashMap<Class<?>, Object>();
+		put(map, boolean.class, false);
+		put(map, char.class, '\0');
+		put(map, byte.class, (byte) 0);
+		put(map, short.class, (short) 0);
+		put(map, int.class, 0);
+		put(map, long.class, 0L);
+		put(map, float.class, 0f);
+		put(map, double.class, 0d);
+		DEFAULTS = Collections.unmodifiableMap(map);
+	}
+
+	private static <T> void put(Map<Class<?>, Object> map, Class<T> type, T value) {
+		map.put(type, value);
+	}
+
+	/**
+	 * Returns the default value of {@code type} as defined by JLS --- {@code 0} for
+	 * numbers, {@code
+	 * false} for {@code boolean} and {@code '\0'} for {@code char}. For
+	 * non-primitive types and {@code void}, null is returned.
+	 */
+	public static <T> T defaultValue(Class<T> type) {
+		// Primitives.wrap(type).cast(...) would avoid the warning, but we can't use
+		// that from here
+		@SuppressWarnings("unchecked") // the put method enforces this key-value relationship
+		T t = (T) DEFAULTS.get(checkNotNull(type));
+		return t;
+	}
+}