java - 在 .txt 文件中搜索字符串并在 Java 中获取行号和列号

Question

我目前遇到了一个问题。我应该编写一个程序，能够在作为参数给出的 .txt 文件中搜索字符串。程序必须返回找到的字符串的行和列。我正在努力寻找一种方法来实现这一目标，但不知道如何继续下去。我会很高兴收到你的来信。

这是我处理任务的尝试:- 我考虑过通过缓冲读取器将文件内容保存在字符串数组中，但这似乎不起作用，因为我无法从一开始就定义数组的长度- 我还考虑过通过缓冲阅读器将文件内容保存在一个字符串中，然后将这个字符串拆分为字符。但是，我不确定那时我将如何检索原始文件中的行。

这是我目前的非功能代码:

public class StringSearch{
    public static void main(String[] args){
        if(args.length > 0){
            BufferedReader br = null;
            String text = null;
            try{
                br = new BufferedReader(new FileReader(args[0]));
                // attempt of saving the content of the "argument" file in a string array and then in a        string
                String[] lines = new String[]; // I know this does not work like this 
                for( int i = 0; i < lines.length; i++){
                    lines[i] = br.readLine;
                    text = text + lines[i];
                    i++;
                }
                text.split("\r\n");

            } catch (IOException ioe){
                ioe.printStackTrace();
            } finally{
                if (br != null) {
                    try{
                        br.close();
                    }catch (IOException ioe){
                        ioe.printStackTrace();
                    }
                }


            }

        }
    }
}

Answer 1

您可以按如下方式进行:

import java.io.File;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        if (args.length != 2) {
            System.out.println("The correct syntax to use this program is: java Main <filename.txt> <text-to-search>");
            return;
        }
        Scanner scanner;
        File file = new File(args[0]);
        int rowCount = 1, index;
        String line;

        // Map to collect row and col info of the search string
        Map<String, String> lineColMap = new HashMap<String, String>();

        if (!file.exists()) {
            System.out.println("The file, " + args[0] + " does not exist");
            return;
        }
        try {
            scanner = new Scanner(file);
            while (scanner.hasNextLine()) {// Loop until the last line in the file
                line = scanner.nextLine();// Read a line from the file
                index = line.indexOf(args[1]);// Find if the string exists in the line
                if (index != -1) {// If the string exists
                    // Put the row and col info of the search string into the map
                    lineColMap.put("Row: " + rowCount, "Column: " + index);
                }
                rowCount++;// Increase the row count
            }
        } catch (Exception e) {
            System.out.println("Error occured while processing the file");
            e.printStackTrace();
        }
        if (lineColMap.entrySet().size() > 0) {// If there is at least one entry collected into the map
            System.out.println("'" + args[1] + "' exists in " + args[0] + " as follows:");
            for (Map.Entry<String, String> entry : lineColMap.entrySet()) {
                System.out.println(entry.getKey() + ", " + entry.getValue());
            }
        } else {
            System.out.println("'" + args[1] + "' does not exist in " + args[0]);
        }
    }
}

示例运行: java Main input.txt of

'of' exists in input.txt as follows:
Row: 1, Column: 51
Row: 2, Column: 50
Row: 3, Column: 50
Row: 5, Column: 71

input.txt内容如下:

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代码逻辑很通俗，相信第一次看的时候应该能看懂。如有任何疑问，请随时发表评论。