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.store.mail.model; import org.apache.commons.codec.digest.DigestUtils; import com.google.common.base.MoreObjects; import com.google.common.base.Objects; import com.google.common.base.Preconditions; import com.google.common.base.Strings; public class AttachmentId { public static AttachmentId forPayload(byte[] payload) { Preconditions.checkArgument(payload != null); return new AttachmentId(DigestUtils.sha1Hex(payload)); } public static AttachmentId from(String id) { Preconditions.checkArgument(!Strings.isNullOrEmpty(id)); return new AttachmentId(id); } private final String id; private AttachmentId(String id) { this.id = id; } public String getId() { return id; } @Override public boolean equals(Object obj) { if (obj instanceof AttachmentId) { AttachmentId other = (AttachmentId) obj; return Objects.equal(id, other.id); } return false; } @Override public int hashCode() { return Objects.hashCode(id); } @Override public String toString() { return MoreObjects.toStringHelper(this).add("id", id).toString(); } }