java - Java 标识符中的 "connecting characters"是什么？

Question

我正在为 SCJP 阅读，我对此行有疑问:

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

它指出有效的标识符名称可以以连接字符如下划线开头。我认为下划线是唯一有效的选择？还有哪些连接字符？

Answer 1

这里是连接字符的列表。这些是用来连接单词的字符。

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。

int _, ‿, ⁀, ⁔, ︳, ︴, ﹍, ﹎, ﹏, ＿;

---

一个例子。在这种情况下，tp 是列名和给定行的值。

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

double tp = row.getDouble(︴tp︴);

---

以下

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

$ _¢£Ö$ $؋؋৳৻฿‿⁀₠₡₢₢₣₣₤₤₥₧₨₨€€€₫₫₭₭₭ ﹍ ﹎ ﹏ ﹩ ＄ ＿ ￠ ￡ ￥ ￦