String array from file to ComboBox

[cselic]

Hi.
I have a file: myFile.txt
In that file is in every line: name + '\t' + numberOfYears.

I want to get String array of names and put that names to be ComboBox items.

I'm thinking like that:
1. make class ReadFromFile
2. in that class write a function getNames which opens a file, read line by line
and get from each line name and put it in string array. This function return that string array.
3. make class MyPanel extends JPanel
4. in MyPanel create object ReadFromFile and call function getNames.
5. use return value from this function to populate items in ComboBox.

please tell me your thinking, or share some ideas with me.
Please give me advice, or tell me better way of thinking and planing, or tell me is something wrong with my planning.

[JosAH]

Your thinking is fine, go ahead.

kind regards,

Jos

[cselic]

With String[] it goes with null exception, so I change it to ArrayList.

I've written first part of code in a small program:

import java.io.BufferedReader;
import java.io.FileReader;

import java.util.ArrayList;

import java.io.FileNotFoundException;
import java.io.IOException;

public class StudNames {
	public static void main(String[] args) {
		ReadFromFile namesOfStudents = new ReadFromFile();
		ArrayList<String> students = namesOfStudents.getNames("students.txt");
		System.out.println(students.toString());
	}

}

class ReadFromFile {
	int indexOfNames = 0;
	ArrayList<String> names = new ArrayList<String>();
	
	public ArrayList<String> getNames(String filename) {
		BufferedReader reader = null;
		try {
			int positionOfTab = 0;
			String lineOfString;
			reader = new BufferedReader(new FileReader(filename));
			while((lineOfString = reader.readLine()) != null) {
				positionOfTab = lineOfString.indexOf('\t');
				
				if(positionOfTab > 0)
					names.add(lineOfString.substring(0, positionOfTab));
				else
					names.add("");
			}
		} catch(FileNotFoundException e) {
			e.printStackTrace();
		} catch(IOException e) {
			e.printStackTrace();
		}
		
		return names;
	}
}

when I write the whole program will post it here.

[cselic]

program that reads data from the file "students.txt" (format of students.txt is:
studentName + '\t' + age).
Then it takes all the studentNames and places as ComboBox item.

import java.io.BufferedReader;
import java.io.FileReader;

import java.util.ArrayList;

import java.io.FileNotFoundException;
import java.io.IOException;

import javax.swing.JFrame;
import javax.swing.JComboBox;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class StudNames {
	public static void main(String[] args) {
		ReadFromFile namesOfStudents = new ReadFromFile();
		
		SwingUtilities.invokeLater(new Runnable() {
			
			@Override
			public void run() {
				StudFrame frame = new StudFrame("Students names");
				frame.showGUI();
			}
		});
	}

}

class StudFrame extends JFrame {
	PanelWithComboBox panel = new PanelWithComboBox();
	
	public StudFrame(String name) {
		setTitle(name);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setSize(300,300);
		add(panel);
	}
	
	public void showGUI() {
		setVisible(true);
	}
}

class PanelWithComboBox extends JPanel {
	JComboBox comboBox;
	
	ReadFromFile rff = new ReadFromFile();
	
	
	public PanelWithComboBox() {
		ArrayList<String> listOfNames = rff.getNames("students.txt");
		comboBox = new JComboBox(listOfNames.toArray());
		add(comboBox);
	}
}

class ReadFromFile {
	int indexOfNames = 0;
	ArrayList<String> names = new ArrayList<String>();
	
	public ArrayList<String> getNames(String filename) {
		BufferedReader reader = null;
		try {
			int positionOfTab = 0;
			String lineOfString;
			reader = new BufferedReader(new FileReader(filename));
			while((lineOfString = reader.readLine()) != null) {
				positionOfTab = lineOfString.indexOf('\t');
				
				if(positionOfTab > 0)
					names.add(lineOfString.substring(0, positionOfTab));
				else
					names.add("");
			}
		} catch(FileNotFoundException e) {
			e.printStackTrace();
		} catch(IOException e) {
			e.printStackTrace();
		}
		
		return names;
	}
}