Question

我有一个tokenizer，我需要提取每个标记，并将其写入输出文件。令牌必须以某种逻辑顺序存在（根据语言语法）。因此，我还必须验证令牌顺序遵循语法规范。目前，我正在通过使用类似于assert的方法来执行此操作，该方法会使用适当的消息抛出异常。这是代码：

public void compileVarDec() throws IOException, IllegalSyntaxException {

    output.write("<varDec>\n");

    verifyStaticField();
    output.write("<keyword> " + tokenizer.keyWord() + " </keyword>\n");
    tokenizer.advance();

    verifyLegalType();
    output.write("<keyword> " + tokenizer.keyWord() + " </keyword>\n");
    tokenizer.advance();

    verifyIdentifier();
    output.write("<identifier> " + tokenizer.identifier() + " </identifier>\n");
    tokenizer.advance();

    verifySymbol(JackTokenizer.SEMI_COLON);
    output.write("<symbol> " + tokenizer.symbol() + " </symbol>\n");
    tokenizer.advance();

    output.write("</varDec>\n");
}

private void verifySymbol(char token) throws IllegalSyntaxException {
    if (tokenizer.tokenType() != JackTokenizer.TOKEN_TYPE.SYMBOL ||
            tokenizer.symbol() != token)
        throw new IllegalSyntaxException("Expected the symbol '" + token + "'");
}

private void verifyStaticField() throws IllegalSyntaxException {
    if (tokenizer.tokenType() != JackTokenizer.TOKEN_TYPE.KEYWORD ||
            (!tokenizer.keyWord().equals(JackTokenizer.FIELD) &&
                    !tokenizer.keyWord().equals(JackTokenizer.STATIC))) {
        throw new IllegalSyntaxException("Expected 'static' or 'field'");
    }
}

private void verifyLegalType() throws IllegalSyntaxException {
    if (tokenizer.tokenType() != JackTokenizer.TOKEN_TYPE.KEYWORD ||
            (!tokenizer.keyWord().equals(JackTokenizer.INT) &&
                    !tokenizer.keyWord().equals(JackTokenizer.CHAR) &&
                    !tokenizer.keyWord().equals(JackTokenizer.BOOLEAN)))
        throw new IllegalSyntaxException("Expected a legal type");
}

private void verifyIdentifier() throws IllegalSyntaxException {
    if (tokenizer.tokenType() != JackTokenizer.TOKEN_TYPE.IDENTIFIER)
        throw new IllegalSyntaxException("Expected an identifier");
}

以这种方式验证输入是否被视为良好做法？要调用一个检查输入的方法，然后，如果它无效，将抛出异常，当前方法将忽略抛出的异常并将其传递给它？如果您有其他建议我会很高兴听到。注意，我想避免两次运行令牌，所以我必须验证输入并同时写入输出

java - 使用类似断言的方法验证输入有效性

0 个答案: