How to search a file for a certain date and time (inputted from user) in java

I am trying to figure out how I would go about searching a .txt file for a certain date and time that is given by the user. Currently my code does this:

PRINT "Enter the date of the task: "
READ into task_date (string)
PRINT "Enter the time of the task: "
READ into task_time (string)
PRINT "Enter the name of the task: "
READ into task_name (string)
LOAD tasks.txt file

I want to be able to read the data from the user in those three steps (yes i know it would probably be better to do it in one step but this is more of a proof of concept to a friend), then search a the tasks.txt file for a space to insert the task_date + task_time + task_name. Any help would be appreciated. Thanks

Edit:
Ok, I am creating a calendar app that is currently terminal based.
What it does is it takes the user inputs task date/time/name and appends it in the correct position in a file called tasks.txt (the file example is below)

10-6-2020 6:30 am Wake up
10-6-2020 7:00 am Take mom to school
10-6-2020 7:30 am arrive back home
10-6-2020 8:30 am leave for class
10-6-2020 9:00 am arrive on campus
10-6-2020 12:00 pm leave campus
10-6-2020 12:30 pm arrive back home
10-6-2020 1:00 pm Meeting with advisors

So lets say the user inputs '10-06-2020 10:00 am Walk into class'
I want the code to insert that line between 9:00 am and 12:00 pm

I apologize if the first question i posted was incomplete.

Edit 2:
My question isn't for others to code for me. My question is can anyone point me in the direction of how to append a string in the correct position of the txt file. (If you're confused look above). Again I'm not asking anyone to code it for me.

      System.out.print("Enter the date of the task: ");
// //     STRING task_time = INPUT
      task_date = scan.nextLine();
// //     PRINT "Enter the name of the task: "
      System.out.print("Enter the time of the task: ");
// //     STRING task_name = INPUT
      String task_time = scan.nextLine();
// //     CREATE new_task = task_date + task_time + task_name (STRING)
      // String new_task = task_date;
      System.out.print("Enter the name of the task: ");
      // STRING task_date = INPUT
      String task_name = scan.nextLine();
      String task = task_date + " " + task_time  + " " + task_name;
      System.out.println(task);
//     LOADFILE tasks.txt
      String search_date = task_date;
      String search_time = task_time;
      int lineNumber = 0;
      File taskstxt = new File("tasks.txt");
      Scanner filereader = new Scanner(taskstxt);
//     SEARCH tasks.txt for corresponding date and time
      while (filereader.hasNextLine()) {
        final String lineFromFile = filereader.nextLine();
        if (lineFromFile.contains(search_date)) {

        }
      }

above is the code snippet in question. I want to search the txt file for for the date and time inputted by the user, and if it exists print "you have a task for that time already", if it doesn't exist I want to append the file with the task date/time/name. I'm sorry if this is confusing for anyone (I find it hard sometimes to write out exactly what I'm thinking)

Q: How do a build a "Calendar app" in Java?

A: Per your design above, your app will have the following:

1. A UI for adding records (currently command line, but you might want to consider a web UI, Android, Swing or other alternatives)
2. A UI for displaying records
3. A data store for saving records (currently a text file, but you might want to consider a "structured text" format like JSON or XML, or a database).

Q: How do I save a new calendar record in the correct position?

A: I would suggest:

1. Write a "TaskList" class for holding your calendar records.

   SIMPLE EXAMPLE:

   public class TaskList {
     public List<TaskRecord> tasks;
   
     public void save(string filename) { ... }
     public void load(string filename) { ... }
   }
   

2. Write a "TaskRecord" class for individual tasks:

   SIMPLE EXAMPLE:

   public class TaskRecord {
     public Date dateTime;
     public String taskText;
   }
   

3. It's important to keep the "date" separate from your "text" in your class.

   If you want a simple text file, and you want everything on the same line, then choose a delimiter that makes it easy to parse. For example, you can separate "date" and "time" with a tab (\t):

   10-6-2020 6:30 am\tWake up

4. It might be unimportant to "insert the record in the right place" until you're ready to "save" the updated file. You can simply "sort()" (by date/time) before you "write()":

   SIMPLE EXAMPLE:

    public class TaskRecord implements  Comparator<Date> {
      public Date dateTime;
      public String taskText;
   
      @Override
      public int compare(TaskRecord a, TaskRecord b) {
        return a.datetime.compareTo(b.datetime);
      }
    }
   

5. If you really wanted to sort each new record as you insert it, you'd still probably want to implement "Comparator" (as above). You'd loop through your list until you find a time/date >= your new date, then List.add() at that index.

6. You'd probably also want to add methods to your "TaskList" class to add, modify and/or delete records.

7. "Encapsulation" can make your classes more robust. You want to hide everything about the class that's not "essential" from users of that class

   SIMPLE EXAMPLE:

      public class TaskRecord implements  Comparator<Date> {
        private Date dateTime;
        private String taskText;
   
        // Initialize object state in constructor
        public TaskRecord(Date dateTime, String taskText) {
          this.dateTime = dateTime;
          this.taskText = taskText;
        }
   
        // "Getter" methods for read-only access
        Date getDateTime() { return dateTime; }
        String getTaskText() { return taskText; }
   
        @Override
        public int compare(TaskRecord a, TaskRecord b) {
          return a.datetime.compareTo(b.datetime);
        }
   
      }
   

'Hope that helps ... at least a little