java - 线程 "main"java.util.regex.PatternSyntaxException : Unmatched closing 中出现异常

Question

我正在尝试使用代码注释中显示的语法翻译回句子“b((aa)a)b$”。当我尝试运行它时，出现以下错误。这似乎是字符串分割方法的错误，但我不知道如何修复它。有什么建议么？谢谢。

run:

b((a)a)b$

Exception in thread "main" java.util.regex.PatternSyntaxException: Unmatched closing ')' near index 3

a)

^ at java.util.regex.Pattern.error(Pattern.java:1955) at java.util.regex.Pattern.compile(Pattern.java:1700) at java.util.regex.Pattern.(Pattern.java:1351) at java.util.regex.Pattern.compile(Pattern.java:1028) at java.lang.String.split(String.java:2367) at exercise3.GrammarTest.parser(GrammarTest.java:28) at exercise3.GrammarTest.parser(GrammarTest.java:48) at exercise3.GrammarTest.main(GrammarTest.java:62)

Java Result: 1

BUILD SUCCESSFUL (total time: 1 second)

//grammar
//<P> → <S>$ (P is the start symbol)
//<S> → b<M>b
//<M> → (<L>
//<M> → a
//<L> → <M> a)


public static String parser(String original, String sym, String rep){
    if( !(original.contains(sym))){
        return original;
    }

    String str = "";
    String [] parts = original.split(sym, 2);

    str = parts[0] + rep + parts[1];

    System.out.println(str);
    return str;
}           

public static String parser(String str){
    String [] sym = new String[5];
    //recursive                //b((aa)a)b$
    str = parser(str, "a", "<M>"); //b((<M>a)a)b$
    str = parser(str, "<M>a)", "<L>"); //b((<L>a)b$
    str = parser(str, "(<L>", "<M>"); //b(<M>a)b$
    str = parser(str, "<M>a)", "<L>"); //b(<L>b$
    str = parser(str, "(<L>", "<M>"); //b<M>b$
    str = parser(str, "b<M>b", "<S>"); //<S>$
    str = parser(str, "<S>$", "<P>"); //<P>

    System.out.println(str);

    return str;
}

public static void main(String[] args) {
    String str = " b((aa)a)b$ ";
    str = parser(str);       

}

Answer 1

当你想匹配(时，你必须将其转义为\\(，因为(是一个组的开始对于正则表达式。对于懒惰的人，Java 为此提供了一个外观: Pattern.quote("(a");/* 为您提供\\(a */