Question

我有一个非常简单的使用StreamTokenizer的tokenizer，它将数学表达式转换为它们各自的组件（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，它将分为[T，_，1]，我想将其作为[T_1]返回。

我试图使用变量来检查最后一个字符是否是下划线，如果是，则将下划线附加到list.Size-1上，但它看起来像一个非常笨重且低效的解决方案。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;

Answer 1

这就是你想要的。

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

这使_可识别为单词的一部分。

附录：

这构建并运行：

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]

Answer 2

StringTokenizer可能更适合。如果是这样，以下是您使用它的方式：

import java.util.ArrayList; import java.util.List; import 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);
    }
}

打印出来：

[T_1, 1, *, bar]

Java Tokenization：将下划线分隔的任何内容视为一个单词

2 个答案: