Java tutorial
/* * Copyright 2014 The Netty Project * * The Netty Project 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 io.netty.handler.codec.mqtt; import java.util.Collections; import java.util.HashMap; import java.util.Map; /** * Return Code of {@link MqttConnAckMessage} */ public enum MqttConnectReturnCode { CONNECTION_ACCEPTED((byte) 0x00), CONNECTION_REFUSED_UNACCEPTABLE_PROTOCOL_VERSION( (byte) 0X01), CONNECTION_REFUSED_IDENTIFIER_REJECTED( (byte) 0x02), CONNECTION_REFUSED_SERVER_UNAVAILABLE( (byte) 0x03), CONNECTION_REFUSED_BAD_USER_NAME_OR_PASSWORD( (byte) 0x04), CONNECTION_REFUSED_NOT_AUTHORIZED((byte) 0x05); private static final Map<Byte, MqttConnectReturnCode> VALUE_TO_CODE_MAP; static { final Map<Byte, MqttConnectReturnCode> valueMap = new HashMap<Byte, MqttConnectReturnCode>(); for (MqttConnectReturnCode code : values()) { valueMap.put(code.byteValue, code); } VALUE_TO_CODE_MAP = Collections.unmodifiableMap(valueMap); } private final byte byteValue; MqttConnectReturnCode(byte byteValue) { this.byteValue = byteValue; } public byte byteValue() { return byteValue; } public static MqttConnectReturnCode valueOf(byte b) { if (VALUE_TO_CODE_MAP.containsKey(b)) { return VALUE_TO_CODE_MAP.get(b); } throw new IllegalArgumentException("unknown connect return code: " + (b & 0xFF)); } }