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我正在处理一项任务，您必须在其中获取包含一些代码的文件并识别其中的令牌并以特定格式输出它们。到目前为止，我已经从文件中获取了字符并将其添加到数组列表中。现在我无法想出在文件中查找特定标记的逻辑。我知道您首先必须创建一个循环来遍历数组列表。我在analyzeForTokens 的评论中有我的逻辑大纲。我不确定如何让它通过并只附加每种类型一次，因为一旦 for 循环的第一次迭代它检查，然后它在第二次迭代中再次检查，所以我觉得会有重叠。我将如何解决这个问题？

import java.util.ArrayList;
import java.util.Scanner;
import java.io.*;
import java.lang.Character;

public class Main {

    /*
        Constants for specific tokens that can be identified easily.
     */
    final Character LPAREN = '(';
    final Character RPAREN = ')';
    final Character ADD_OP[] = {'+', '-'};
    final String MULT_OP[] = {"*", "/", "//", "%"};
    final Character ASSIGN[] = {':', '='};
    final Character IDENTIFIERS[] ={'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'j', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};
    final int NUMBERS[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};

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

        Scanner input = new Scanner(System.in); //Scanner for taking input from the user

        String fileName;
        System.out.println("Enter the name of the file.");
        fileName = input.next();

        fileExists(fileName); // Checks to see if the file exists

        ArrayList<Character> arrayOfTokens = new ArrayList<Character>();
        readToArray(arrayOfTokens, fileName);

        for(int i = 0; i < arrayOfTokens.size(); i++) {
            System.out.print(arrayOfTokens.get(i) + ", ");
        }

    }

    /*
        readToArray goes through a file and adds all its elements in individual character form. It is stored into an arraylist and it is then returned
        @param storeChar: This is an arraylist of characters that the characters will be saved into and then returned.
        @param fileName: The filename that you want to take the data from.
     */
    private static ArrayList<Character> readToArray(ArrayList<Character> storeChar, String fileName) throws IOException {
        /*
            Block of code to setup the fileInput stream to take in data from the file. Reads character by character and stores into an arraylist.
            int atChar: the current character the reader is at. Returns in int format (Need to be converted to character later on)
            int currentIndex: to add a character to an index. Increments until no more characters are left
         */
        FileInputStream fileInput = new FileInputStream(fileName);
        int atChar;
        int currentIndex = 0;

        /*
            Loop to go through and add the converted character from an int to the arraylist.
            Loops until atChar returns -1 which means no more characters in file.
         */
        while((atChar = fileInput.read()) != -1) {
            storeChar.add(currentIndex, (char)(atChar));
            currentIndex++;
        }
        fileInput.close();
        return storeChar;
    }

    /*
        fileExists method makes sure the file the user enters exists in the system. If it doesn't then the program will terminate before any further code is executed.
        @param fileName: Takes in a string paramater of the file name that you want to if it exists.
     */
    private static void fileExists(String fileName) {

        boolean ifExists; //Boolean statement that will later be set to the value of whether the file exists or not

        File file = new File(fileName);
        ifExists = file.exists();

        if(ifExists == false) {
            System.out.println("Unable to find the file. Will now close the program.");
            System.exit(0);
        }
    }

    private static ArrayList<String> analyzeForTokens(ArrayList<Character> tokens, Character LPAREN, Character RPAREN, Character ADD_OP, String MULTI_OP, Character ASSIGN, Character IDENTIFIERS, int NUMBERS) {

        ArrayList<String> indentified = new ArrayList<String>();

        for(int i = 0; i < tokens.size(); i++) { //first for loop go through the whole array list 
            //if statement to check if CURRENT character is an identifier, number, lparam, rparam etc...
                //Another loop to go until you find a white space. Then concatinate all indexes from first index to white space into new string
                //if started with indentifer param then it will take the appended string then append < identifierType >, identifierType (As long as identifier longer than one character)
                //if string only consists of one string then it is an id append <id>, id
                //if number converts the character integer and compares and so on....
            //Once returned just printout the values of the arraylist since they should be appended int he correct format

        }

        return indentified;
    }
}

编辑：输入文件和输出应该是这样的。输入：

read a
read b
c := a + b + 3
write c

输出：

<read>, read
<id>, a
<read>, read
<id>, b
<id>, c
<assign>, :=
<id>, a
<add_op>, +
<id>, b
<add_op>, +
<number>, 3
<write>, write
<id>, c
4

0 回答 0