什么是“连接字符”在Java标识符？ [英] What are "connecting characters" in Java identifiers?

问题描述

我正在阅读SCJP，我对这一行有疑问：

I am reading for SCJP and I have a question regarding this line:

标识符必须以字母，货币字符开头（ $），或
连接字符，如下划线（_）。标识符不能
以数字开头！

Identifiers must start with a letter, a currency character ($), or a connecting character such as the underscore ( _ ). Identifiers cannot start with a number!

它表明有效的标识符名称可以以连接字符开头例如下划线。我认为下划线是唯一有效的选择吗？还有哪些连接字符？

It states that a valid identifier name can start with a connecting character such as underscore. I thought underscores were the only valid option? What other connecting characters are there?

推荐答案

这是一个连接字符列表。这些是用于连接单词的字符。

Here is a list of connecting characters. These are characters used to connect words.

http://www.fileformat.info/info/unicode/category/Pc/list.htm

U+005F _ LOW LINE
U+203F ‿ UNDERTIE
U+2040 ⁀ CHARACTER TIE
U+2054 ⁔ INVERTED UNDERTIE
U+FE33 ︳ PRESENTATION FORM FOR VERTICAL LOW LINE
U+FE34 ︴ PRESENTATION FORM FOR VERTICAL WAVY LOW LINE
U+FE4D ﹍ DASHED LOW LINE
U+FE4E ﹎ CENTRELINE LOW LINE
U+FE4F ﹏ WAVY LOW LINE
U+FF3F ＿ FULLWIDTH LOW LINE

这在Java 7上编译。

This compiles on Java 7.

int _, ‿, ⁀, ⁔, ︳, ︴, ﹍, ﹎, ﹏, ＿;

---

一个例子。在这种情况下， tp 是列的名称和给定行的值。

---

An example. In this case tp is the name of a column and the value for a given row.

Column<Double> ︴tp︴ = table.getColumn("tp", double.class);

double tp = row.getDouble(︴tp︴);

---

以下

---

The following

for (int i = Character.MIN_CODE_POINT; i <= Character.MAX_CODE_POINT; i++)
    if (Character.isJavaIdentifierStart(i) && !Character.isAlphabetic(i))
        System.out.print((char) i + " ");
}

打印

$ _¢¥¥؋৲৳૱฿฿₣₤₥₨₨₨₩₩₩₫₯₰₰₸₸₸₸₸₸﷼﷼﷼﷼﷼﹎﹎﹎ $ $ _¢£¥₩

$ _ ¢ £ ¤ ¥ ؋ ৲ ৳ ৻ ૱ ௹ ฿ ៛ ‿ ⁀ ⁔ ₠ ₡ ₢ ₣ ₤ ₥ ₦ ₧ ₨ ₩ ₪ ₫ € ₭ ₮ ₯ ₰ ₱ ₲ ₳ ₴ ₵ ₶ ₷ ₸ ₹ ꠸ ﷼ ︳ ︴ ﹍ ﹎ ﹏ ﹩ ＄ ＿ ￠ ￡ ￥ ￦

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