Update #0 - First Release

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

@@ -0,0 +1,103 @@
+/*
+ * Copyright (C) 2011 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.Set;
+
+import javax.annotation.Nullable;
+
+import com.google.common.annotations.GwtCompatible;
+
+/**
+ * Implementation of an {@link Optional} containing a reference.
+ */
+@GwtCompatible
+final class Present<T> extends Optional<T> {
+	private final T reference;
+
+	Present(T reference) {
+		this.reference = reference;
+	}
+
+	@Override
+	public boolean isPresent() {
+		return true;
+	}
+
+	@Override
+	public T get() {
+		return reference;
+	}
+
+	@Override
+	public T or(T defaultValue) {
+		checkNotNull(defaultValue, "use Optional.orNull() instead of Optional.or(null)");
+		return reference;
+	}
+
+	@Override
+	public Optional<T> or(Optional<? extends T> secondChoice) {
+		checkNotNull(secondChoice);
+		return this;
+	}
+
+	@Override
+	public T or(Supplier<? extends T> supplier) {
+		checkNotNull(supplier);
+		return reference;
+	}
+
+	@Override
+	public T orNull() {
+		return reference;
+	}
+
+	@Override
+	public Set<T> asSet() {
+		return Collections.singleton(reference);
+	}
+
+	@Override
+	public <V> Optional<V> transform(Function<? super T, V> function) {
+		return new Present<V>(checkNotNull(function.apply(reference),
+				"the Function passed to Optional.transform() must not return null."));
+	}
+
+	@Override
+	public boolean equals(@Nullable Object object) {
+		if (object instanceof Present) {
+			Present<?> other = (Present<?>) object;
+			return reference.equals(other.reference);
+		}
+		return false;
+	}
+
+	@Override
+	public int hashCode() {
+		return 0x598df91c + reference.hashCode();
+	}
+
+	@Override
+	public String toString() {
+		return "Optional.of(" + reference + ")";
+	}
+
+	private static final long serialVersionUID = 0;
+}