Java 完全限定的类名(假设为N")具有以下结构

A Java fully qualified class name (lets say "N") has the structure

N.N.N.N

N"部分必须是 Java 标识符.Java 标识符不能以数字开头，但在首字符之后可以使用字母和数字、下划线或美元符号的任意组合:

The "N" part must be a Java identifier. Java identifiers cannot start with a number, but after the initial character they may use any combination of letters and digits, underscores or dollar signs:

([a-zA-Z_$][a-zA-Zd_$]*.)*[a-zA-Z_$][a-zA-Zd_$]*
------------------------    -----------------------
          N                           N

它们也不能是保留字(例如 import、true 或 null).如果您只想检查合理性，以上就足够了.如果您还想检查有效性，您还必须对照保留字列表进行检查.

They can also not be a reserved word (like import, true or null). If you want to check plausibility only, the above is enough. If you also want to check validity, you must check against a list of reserved words as well.

Java 标识符可以包含任何 Unicode 字母而不是仅限拉丁语".如果您也想检查这一点，请使用 Unicode 字符类:

Java identifiers may contain any Unicode letter instead of "latin only". If you want to check for this as well, use Unicode character classes:

([p{Letter}_$][p{Letter}p{Number}_$]*.)*[p{Letter}_$][p{Letter}p{Number}_$]*

或者，简称

([p{L}_$][p{L}p{N}_$]*.)*[p{L}_$][p{L}p{N}_$]*

Java 语言规范，(第 3.8 节) 包含有关有效标识符名称的所有详细信息.

The Java Language Specification, (section 3.8) has all details about valid identifier names.

另请参阅此问题的答案:Java Unicode 变量名称

Also see the answer to this question: Java Unicode variable names