如何在一个Java语句中连接静态最终String数组


How to concatenate static final String arrays in one Java statement

C宏可以很容易地解决我的问题…但是，Java似乎需要代码来实现声明由编译器静态组装的子数组的效果。其目的是能够定义一个全局数组/字符串列表，这些字符串可以在大量类中重用。

使用(邪恶)宏构造

全局.c源文件

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#define GLOBAL_HTML_ATTRIBUTES"accesskey","class","contenteditable","contextmenu","dir","draggable","dropzone","hidden","id","lang","spellcheck","style","tabindex","title","translate"

A.C源文件

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#define A_ELEMENT_ATTRIBUTES"download","href","hreflang","media","name","rel","target","type"

char[] attributes = {GLOBAL_HTML_ATTRIBUTES, A_ELEMENT_ATTRIBUTES};

号

有类似的Java构造吗？

是的，我知道其他一些关于串接字符串数组的问题…这个问题旨在帮助C开发人员适应Java编程习语。

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您可以这样使用流：

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static final String[] GLOBAL_HTML_ATTRIBUTES = {
   "accesskey","class","contenteditable","contextmenu",
   "dir","draggable","dropzone","hidden","id","lang",
   "spellcheck","style","tabindex","title","translate"};

static final String[] A_ELEMENT_ATTRIBUTES = {
   "download","href","hreflang","media","name","rel",
   "target","type"};

static final String[] attributes = Stream.concat(
            Stream.of(GLOBAL_HTML_ATTRIBUTES),
            Stream.of(A_ELEMENT_ATTRIBUTES))
        .collect(Collectors.toList()).toArray(new String[]{});
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使用@realconsoluter提供的洞察力，我重构如下：

用"global"字符串抽象"base"类

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public class Abstract_Html_Element
{
    protected static final List<String> attributes = new ArrayList<String>(Arrays.asList("accesskey","class","contenteditable","contextmenu","dir","draggable","dropzone","hidden","id","lang","spellcheck","style","tabindex","title","translate"));

    public Abstract_Html_Element()
    {
        super();
    }
}

。

具有静态初始化块的子类

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public class A_Element extends Abstract_Html_Element
{
    public static final List<String> attributes = new ArrayList<String>(Arrays.asList("download","href","hreflang","media","name","rel","target","type"));

    {
        A_Element.attributes.addAll(Abstract_Html_Element.attributes);
    }

    public A_Element()
    {
        super();
    }
}

这很干净，很容易理解…并且每次执行时只初始化每个列表一次…(最佳实践？)

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这是我觉得美学上令人满意的方法(在一个未成型的C开发人员的眼中，从后面看)：

定义"全局"字符串所在的基类(如下所示)

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public class Abstract_Html_Element
{
    private static final List<String> attributes = new ArrayList<String>(Arrays.asList("accesskey","class","contenteditable","contextmenu","dir","draggable","dropzone","hidden","id","lang","spellcheck","style","tabindex","title","translate"));

    public Abstract_Html_Element(final List<String> attributes)
    {
        super();

        if (null != attributes)
        {
            Abstract_Html_Element.attributes.addAll(attributes);
        }
    }
}

号

然后在实现子类中传递要连接的字符串的数组列表(如下所示)：

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public class A_Element extends Abstract_Html_Element
{
    public static final List<String> attributes = new ArrayList<String>(Arrays.asList("download","href","hreflang","media","name","rel","target","type"));

    public A_Element()
    {
        super(attributes);
    }
}

奇怪的是，通过传递的属性可以很高兴地连接到私有的最终列表属性，这些属性不是在类的实例中引用的，而是在抽象类本身中引用的-这向我暗示了我想要达到的效果，即在子类…我不知道如何检验我的假设…但是，如果编译器真的能够以"单例"的方式附加字符串数组，那么学习它是很有趣的…

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