java - 使用antlr检查方法是否有注释

Question

更改为Java.g4

文件开头

grammar Java;


@lexer::members {
    public static final int WHITESPACE = 1;
    public static final int COMMENTS = 2;
}

文件结束

//
// Whitespace and comments
//

WS  :  [ \t\r\n\u000C]+ -> channel(WHITESPACE) ;  // channel(1)

COMMENT    :   '/*' .*? '*/' -> channel(COMMENTS)  ; // channel(2)

LINE_COMMENT    :   '//' ~[\r\n]* -> channel(COMMENTS) ;   // channel(2)

尝试将注释和空白发送到不同的 channel ，如《The Definitive ANTLR 4》一书中所做的那样引用》第12.1章在不同 channel 上广播代币

执行antlr4 Java.g4时显示以下错误

java org.antlr.v4.Tool Java.g4
    warning(155): Java.g4:1017:35: rule WS contains a lexer command with an unrecognized constant value; lexer interpreters may produce incorrect output
    warning(155): Java.g4:1019:40: rule COMMENT contains a lexer command with an unrecognized constant value; lexer interpreters may produce incorrect output
    warning(155): Java.g4:1021:45: rule LINE_COMMENT contains a lexer command with an unrecognized constant value; lexer interpreters may produce incorrect output

我没看出什么问题？

Answer 1

您应该替换以下片段:

@lexer::members {
    public static final int WHITESPACE = 1;
    public static final int COMMENTS = 2;
}

带字符串:

channels { WHITESPACE, COMMENTS }