2

我有一个使用 StreamTokenizer 的非常简单的标记器,它将数学表达式转换为它们的单独组件(如下)。我遇到的问题是,如果表达式中有一个名为 T_1 的变量,它将拆分为 [T,_,1],我想将其返回为 [T_1]。

我尝试使用变量来检查最后一个字符是否为下划线,如果是,则将下划线附加到 list.Size-1 上,但这似乎是一个非常笨拙且效率低下的解决方案。有没有办法做到这一点?谢谢!

        StreamTokenizer tokenizer = new StreamTokenizer(new StringReader(s));
        tokenizer.ordinaryChar('-'); // Don't parse minus as part of numbers.
        tokenizer.ordinaryChar('/'); // Don't parse slash as part of numbers.
        List<String> tokBuf = new ArrayList<String>();
        while (tokenizer.nextToken() != StreamTokenizer.TT_EOF) //While not the end of file 
        {
            switch (tokenizer.ttype) //Switch based on the type of token
            {
            case StreamTokenizer.TT_NUMBER: //Number
                tokBuf.add(String.valueOf(tokenizer.nval));
                break;
            case StreamTokenizer.TT_WORD: //Word
                tokBuf.add(tokenizer.sval);
                break;
            case '_':
                tokBuf.add(tokBuf.size()-1, tokenizer.sval);
                break;
            default: //Operator
                tokBuf.add(String.valueOf((char) tokenizer.ttype));
            }
        }

        return tokBuf;
4

2 回答 2

4

这就是你想要的。

tokenizer.wordChars('_', '_');

这使得 _ 可识别为单词的一部分。

附加物:

这将构建并运行:

public static void main(String args[]) throws Exception {
    String s = "abc_xyz abc 123 1 + 1";
    StreamTokenizer tokenizer = new StreamTokenizer(new StringReader(s));
    tokenizer.ordinaryChar('-'); // Don't parse minus as part of numbers.
    tokenizer.ordinaryChar('/'); // Don't parse slash as part of numbers.
    tokenizer.wordChars('_', '_'); // Don't parse slash as part of numbers.


    List<String> tokBuf = new ArrayList<String>();
    while (tokenizer.nextToken() != StreamTokenizer.TT_EOF) //While not the end of file 
    {
        switch (tokenizer.ttype) //Switch based on the type of token
        {
        case StreamTokenizer.TT_NUMBER: //Number
            tokBuf.add(String.valueOf(tokenizer.nval));
            break;
        case StreamTokenizer.TT_WORD: //Word
            tokBuf.add(tokenizer.sval);
            break;
        default: //Operator
            tokBuf.add(String.valueOf((char) tokenizer.ttype));
        }
    }
    System.out.println(tokBuf);
}

run:
[abc_xyz, abc, 123.0, 1.0, +, 1.0]
于 2014-09-26T18:59:46.473 回答
0

StringTokenizer可能更合适。如果是这样,这是你如何使用它:

导入 java.util.ArrayList;导入 java.util.List;导入 java.util.StringTokenizer;

public class Solution {

    public static void main(String args[]) throws Exception {
        StringTokenizer tokenizer = new StringTokenizer("T_1 1 * bar");
        List<String> tokBuf = new ArrayList<String>();
        while (tokenizer.hasMoreTokens()) //While not the end of file
        {
            tokBuf.add(tokenizer.nextToken());
        }

        System.out.println(tokBuf);
    }
}

这打印出来:

[T_1, 1, *, bar]
于 2014-09-26T19:04:54.263 回答