Method to find string inside of the text file. Then getting the following lines up to a certain limit

Question

So this is what I have so far :

public String[] findStudentInfo(String studentNumber) {
                Student student = new Student();
                Scan         


        

Answer 1

You can do something like this:

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

When you are reading the file, have you considered reading it line by line? This would allow you to check if your line contains the file as your are reading, and you could then perform whatever logic you needed based on that?

Scanner scanner = new Scanner("Student.txt");
String currentLine;

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

You could use a variable to hold the line number, or you could also have a boolean indicating if you have passed the line that contains your string:

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 3

This will find "Mark Sagal" in Student.txt. Assuming Student.txt contains

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 4

Here is a java 8 method to find a string in a text file:

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 5

Here is the code of TextScanner

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]);
      }
}

It will print text with delimeters

Answer 6

Using the Apache Commons IO API https://commons.apache.org/proper/commons-io/ I was able to establish this using FileUtils.readFileToString(file).contains(stringToFind)

The documentation for this function is at https://commons.apache.org/proper/commons-io/javadocs/api-2.4/org/apache/commons/io/FileUtils.html#readFileToString(java.io.File)