Java tutorial
/**************************************************************** * Licensed to the Apache Software Foundation (ASF) under one * * or more contributor license agreements. See the NOTICE file * * distributed with this work for additional information * * regarding copyright ownership. The ASF licenses this file * * to you 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 org.apache.james.mailbox.model; import com.google.common.base.Objects; import com.google.common.base.Optional; import com.google.common.base.Preconditions; public class MailboxAnnotation { public static MailboxAnnotation nil(MailboxAnnotationKey key) { return new MailboxAnnotation(key, Optional.<String>absent()); } public static MailboxAnnotation newInstance(MailboxAnnotationKey key, String value) { return new MailboxAnnotation(key, Optional.of(value)); } private final MailboxAnnotationKey key; private final Optional<String> value; private MailboxAnnotation(MailboxAnnotationKey key, Optional<String> value) { Preconditions.checkNotNull(key); Preconditions.checkNotNull(value); this.key = key; this.value = value; } public MailboxAnnotationKey getKey() { return key; } public Optional<String> getValue() { return value; } public int size() { if (isNil()) { return 0; } return value.get().length(); } @Override public int hashCode() { return Objects.hashCode(key, value); } public boolean isNil() { return !value.isPresent(); } @Override public boolean equals(Object obj) { if (obj instanceof MailboxAnnotation) { MailboxAnnotation o = (MailboxAnnotation) obj; return Objects.equal(key, o.getKey()) && Objects.equal(value, o.getValue()); } else { return false; } } }