一、Enum使用(1.5使用)

enum在Jdk1.5就已經(jīng)引入了天吓，在Hmily中很多地方都可以看到它的身影贿肩。在日常開發(fā)中enum可以替換很多常量，更符合面向?qū)ο蟮挠^念龄寞。記錄下它的用法：

/*
 * 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
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 * See the License for the specific language governing permissions and
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package com.hmily.tcc.common.enums;

import java.util.Arrays;
import java.util.Objects;
import java.util.Optional;

/**
 * The enum Blocking queue type enum.
 *
 * @author xiaoyu
 */
public enum BlockingQueueTypeEnum {

    /**
     * Linked blocking queue blocking queue type enum.
     */
    LINKED_BLOCKING_QUEUE("Linked"),
    /**
     * Array blocking queue blocking queue type enum.
     */
    ARRAY_BLOCKING_QUEUE("Array"),
    /**
     * Synchronous queue blocking queue type enum.
     */
    SYNCHRONOUS_QUEUE("SynchronousQueue");

    private String value;

    BlockingQueueTypeEnum(final String value) {
        this.value = value;
    }

    /**
     * Gets value.
     *
     * @return the value
     */
    public String getValue() {
        return value;
    }

    /**
     * From string blocking queue type enum.
     *
     * @param value the value
     * @return the blocking queue type enum
     */
    public static BlockingQueueTypeEnum fromString(final String value) {
        Optional<BlockingQueueTypeEnum> blockingQueueTypeEnum =
                Arrays.stream(BlockingQueueTypeEnum.values())
                        .filter(v -> Objects.equals(v.getValue(), value))
                        .findFirst();
        return blockingQueueTypeEnum.orElse(BlockingQueueTypeEnum.LINKED_BLOCKING_QUEUE);
    }

    @Override
    public String toString() {
        return value;
    }
}

這個(gè)Enum非常有代表性汰规，它定義了BlockingQueue的四種類型，需要注意的一點(diǎn)如果Enum有有參構(gòu)造器物邑，那么它一定為private溜哮，并且可以在枚舉類中添加自己的方法，如本例子的fromString(lambda表達(dá)式寫法->轉(zhuǎn)換為下的非lambda寫法)色解。

 
public static BlockingQueueTypeEnum fromString(final String value)
    {
        for(BlockingQueueTypeEnum blockingQueueTypeEnum:BlockingQueueTypeEnum.values())
        {
            if(StringUtils.equals(blockingQueueTypeEnum.getValue(),value))
            {
                return  blockingQueueTypeEnum;
            }
        }
        return BlockingQueueTypeEnum.LINKED_BLOCKING_QUEUE;
    }