不改变类，优化以下方法： public TokenType nextToken() { if (!has_end) { if (index < source.length()) { switch (source.charAt(index++)) { case '.': System.out.println("DOT"); return TokenType.DOT; case '(': System.out.println("LPAREN"); return TokenType.LPAREN; case ')': System.out.println("RPAREN"); return TokenType.RPAREN; case '\\': System.out.println("LAMBDA"); return TokenType.LAMBDA; case ' ': return TokenType.BLANK; default: if ('a' <= source.charAt(index - 1) && source.charAt(index - 1) <= 'z') { int temp = index; while (temp < source.length() && (('a' < source.charAt(temp) && source.charAt(temp) <= 'z') || ('A' <= source.charAt(temp) && source.charAt(temp) <= 'Z') || ('0' <= source.charAt(temp) && source.charAt(temp) <= '9'))) { temp++; } index = temp; System.out.println("LCID"); return TokenType.LCID; } else { System.out.println("EOF"); return TokenType.EOF; } } } else { has_end = true; System.out.println("EOF"); return TokenType.EOF; } } System.out.println("EOF"); return TokenType.EOF; }

可以使用一个HashMap来存储字符和它对应的TokenType，以避免在每次调用nextToken()方法时都进行字符匹配。例如：

private static final Map<Character, TokenType> tokenMap = new HashMap<Character, TokenType>() {{
    put('.', TokenType.DOT);
    put('(', TokenType.LPAREN);
    put(')', TokenType.RPAREN);
    put('\\', TokenType.LAMBDA);
    put(' ', TokenType.BLANK);
}};

public TokenType nextToken() {
    if (!has_end) {
        if (index < source.length()) {
            char c = source.charAt(index++);
            TokenType tokenType = tokenMap.get(c);
            if (tokenType != null) {
                System.out.println(tokenType);
                return tokenType;
            } else if ('a' <= c && c <= 'z') {
                int temp = index;
                while (temp < source.length() && (('a' < source.charAt(temp) && source.charAt(temp) <= 'z')
                        || ('A' <= source.charAt(temp) && source.charAt(temp) <= 'Z')
                        || ('0' <= source.charAt(temp) && source.charAt(temp) <= '9'))) {
                    temp++;
                }
                index = temp;
                System.out.println("LCID");
                return TokenType.LCID;
            } else {
                System.out.println("EOF");
                return TokenType.EOF;
            }
        } else {
            has_end = true;
            System.out.println("EOF");
            return TokenType.EOF;
        }
    }
    System.out.println("EOF");
    return TokenType.EOF;
}

这样，当需要添加新的字符时，只需要在HashMap中添加对应的键值对即可。在每次调用nextToken()方法时，只需查找HashMap中是否存在对应的TokenType即可。