方法查找文本文件内的字符串.然后让下面的行达到一定的极限

Question

这就是我目前看到的内容:

public String[] findStudentInfo(String studentNumber) {
                Student student = new Student();
                Scanner scanner = new Scanner("Student.txt");
                // Find the line that contains student Id
                // If not found keep on going through the file
                // If it finds it stop
                // Call parseStudentInfoFromLine get the number of courses
                // Create an array (lines) of size of the number of courses plus one
                // assign the line that the student Id was found to the first index value of the array
                //assign each next line to the following index of the array up to the amount of classes - 1
                // return string array
}

我知道如何查找文件是否包含我要查找的字符串，但我不知道如何检索其所在的整行。

这是我第一次发帖，如果我做错了什么，请告诉我。

Answer 1

你可以这样做:

File file = new File("Student.txt");
try {
    Scanner scanner = new Scanner(file);
    //now read the file line by line...
    int lineNum = 0;
    while (scanner.hasNextLine()) {
        String line = scanner.nextLine();
        lineNum++;
        if(<some condition is met for the line>) { 
            System.out.println("ho hum, i found it on line " +lineNum);
        }
    }
} catch(FileNotFoundException e) { 
    //handle this
}

Answer 2

使用Apache Commons IO API https://commons.apache.org/proper/commons-io/我能够使用FileUtils.readFileToString(file).contains(stringToFind)建立这个

这个函数的文档在https://commons.apache.org/proper/commons-io/javadocs/api-2.4/org/apache/commons/io/FileUtils.html#readFileToString(java.io.File)

Answer 3

下面是java 8在文本文件中查找字符串的方法:

for (String toFindUrl : urlsToTest) {
        streamService(toFindUrl);
    }
private void streamService(String item) {
        try (Stream<String> stream = Files.lines(Paths.get(fileName))) {
           stream.filter(lines -> lines.contains(item))
                       .forEach(System.out::println);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

Answer 4

在读取文件时，是否考虑过逐行读取?这将允许您检查您的行是否包含正在读取的文件，然后您可以基于此执行所需的任何逻辑。

Scanner scanner = new Scanner("Student.txt");
String currentLine;
while((currentLine = scanner.readLine()) != null)
{
    if(currentLine.indexOf("Your String"))
    {
         //Perform logic
    }
}

您可以使用一个变量来保存行号，或者您也可以使用一个布尔值来指示是否传递了包含字符串的行:

Scanner scanner = new Scanner("Student.txt");
String currentLine;
int lineNumber = 0;
Boolean passedLine = false;
while((currentLine = scanner.readLine()) != null)
{
    if(currentLine.indexOf("Your String"))
    {
         //Do task
         passedLine = true;
    }
    if(passedLine)
    {
       //Do other task after passing the line.
    }
    lineNumber++;
}

Answer 5

这将在Student.txt中找到"Mark Sagal"。假设Student.txt包含

Student.txt

Amir Amiri
Mark Sagal
Juan Delacruz

Main.java

import java.io.BufferedReader;
import java.io.FileReader;
import java.util.ArrayList;
public class Main {
    public static void main(String[] args) {
        final String file = "Student.txt";
        String line = null;
        ArrayList<String> fileContents = new ArrayList<>();
        try {
            FileReader fReader = new FileReader(file);
            BufferedReader fileBuff = new BufferedReader(fReader);
            while ((line = fileBuff.readLine()) != null) {
                fileContents.add(line);
            }
            fileBuff.close();
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
        System.out.println(fileContents.contains("Mark Sagal"));
    }
}

Answer 6

我正在做类似的事情，但在c++中。您需要做的是一次读一行并解析它们(一个一个地检查单词)。我有一个外循环，遍历所有行，里面是另一个循环，遍历所有单词。一旦找到所需的单词，只需退出循环并返回计数器或任何您想要的内容。

这是我的代码。它基本上解析出所有的单词，并将它们添加到"索引"中。然后将word所在的行添加到vector中，并用于引用索引单词中的行(包含文件名、整行和行号)。

ifstream txtFile;
txtFile.open(path, ifstream::in);
char line[200];
//if path is valid AND is not already in the list then add it
if(txtFile.is_open() && (find(textFilePaths.begin(), textFilePaths.end(), path) == textFilePaths.end())) //the path is valid
{
    //Add the path to the list of file paths
    textFilePaths.push_back(path);
    int lineNumber = 1;
    while(!txtFile.eof())
    {
        txtFile.getline(line, 200);
        Line * ln = new Line(line, path, lineNumber);
        lineNumber++;
        myList.push_back(ln);
        vector<string> words = lineParser(ln);
        for(unsigned int i = 0; i < words.size(); i++)
        {
            index->addWord(words[i], ln);
        }
    }
    result = true;
}

Answer 7

下面是TextScanner的代码

public class TextScanner {
        private static void readFile(String fileName) {
            try {
              File file = new File("/opt/pol/data22/ds_data118/0001/0025090290/2014/12/12/0029057983.ds");
              Scanner scanner = new Scanner(file);
              while (scanner.hasNext()) {
                System.out.println(scanner.next());
              }
              scanner.close();
            } catch (FileNotFoundException e) {
              e.printStackTrace();
            }
          }
          public static void main(String[] args) {
            if (args.length != 1) {
              System.err.println("usage: java TextScanner1"
                + "file location");
              System.exit(0);
            }
            readFile(args[0]);
      }
}

它将打印带有分隔符的文本