找出语句中的变量——正则表达式

[code="java"]public class Main {

public static void main(String[] args) throws IOException {


    String str = "ab123_c == 'xx_123_ABC'|| a==1 && ttt != \"aaa\"'\" ||  xxx >= 1.12345 && abc==true && ddd==false";

    String variable = "([a-zA-Z_][a-zA-Z0-9_]*)";
    String keyword = "(true|false)";

    Matcher variableMatcher = Pattern.compile(variable).matcher(str);

    while(variableMatcher.find()) {
        String var = variableMatcher.group(1);
        if(Pattern.matches(keyword, var)) {
           continue; 
        }
        int index = str.indexOf(var);
        boolean isConstString = false;
        do {
            if(isConstString(str, str.indexOf(var) - 1)) {
                isConstString = true;
                break;
            }
            index = str.indexOf(var, index+1); 
        } while(index != -1);

        if(isConstString) {
           continue; 
        }

        System.out.println(var);
    }
}

private static boolean isConstString(String str, int index) {
    if(index <= 0) {
        return false;
    }
    char c = str.charAt(index);

    return c == '\'' || c == '\"';
}

}[/code]

这种方式肯定不好，需要使用如ANTLR 进行词法/语法分析。