/** Convert the stringbuilder into an actual string, then return it */
        String completeMatchList = matchList.toString();
        String [] splitresult;
        String name = matchList.toString();
        splitresult= name.split("\\s");
        //txtbgreenentry.setText(splitresult[0]);
        //txtbyellowentry.setText(splitresult[0]);
        /** System.out.println(splitresult[5]); - this was added to test that the text has been broken down in to individual strings, then it prints off in an array to the console */
                for (int i = 0; i < 18; i++)
        {
            sd.getyh(i).getEmptyMatches();
            sd.getgh(i).getEmptyMatches();
        }
        return completeMatchList;

public class Matchlist
{
 
    private studentdetails sd = new studentdetails();
    /** matchList StringBuilder stores the match list in progress */
    private StringBuilder matchList = new StringBuilder();
 
    private int loop = 0;
    private int matches = 0;
    public Matchlist()
    {
        sd.createstudentdetails();
    }
 
    /** Method to create the actual match list, returns the list as a string */
    public String CreateMatch()
    {
        int g;
        int y;
 
        for (g = 0; g < 4; g++) /** this is for the game */
        {
            for (y = 17; y > -1; y--) /** used for the yellow house */
            {
                /** Check to see if the game is empty */
                if (sd.getgh(y).getGame(g).equals(""))
                {
                    for (int x = 0; x < 18; x++) /** used for the yellow house */
                    {
                        if (sd.getyh(x).getGame(g).equals(""))
                        {
                            if (sd.getgh(y).getC_lass() != sd.getyh(x).getC_lass()) /** used for the green house */
                            {
                                /** Check to see if the person has played the other person */
                                if (sd.getgh(y).checkPlayed(sd.getyh(x).getName()) == false)
                                {
                                    /** Set the game to the name of the opponent played */
                                    sd.getyh(x).changeGame(g, sd.getgh(y).getName());
                                    sd.getgh(y).changeGame(g, sd.getyh(x).getName());
                                    /** Build the match list step by step using append with \n at the end to create a new line */
                                    matchList.append(sd.getyh(x).getName() + " vs " + sd.getgh(y).getName()  +"\n");
                                    matches++; /** add to the matches */
                                    break;
                                }
 
                            }
 
                        }
                    }
                }
            }
 
        }
        /** Convert the stringbuilder into an actual string, then return it */
        String completeMatchList = matchList.toString();
        String [] splitresult;
        String name = matchList.toString();
        splitresult= name.split("\\s");
        //txtbdisplaymatch.setText(splitresult[0]); 
        txtbyellowentry.setText(splitresult[0]);
        /** System.out.println(splitresult[5]); - this was added to test that the text has been broken down in to individual strings, then it prints off in an array to the console */
                for (int i = 0; i < 18; i++)
        {
            sd.getyh(i).getEmptyMatches();
            sd.getgh(i).getEmptyMatches();
        }
 
        return completeMatchList; /** returns the match list that has been completed */ 
    } 
}

a
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
 
public class MyPanel extends JPanel implements ActionListener
{   //add the "implements ActionListener" line so the class knows its going to take an input
 
    private Matchlist ml = new Matchlist();
    private JButton btngenerate;
    public JTextArea txtbdisplaymatch;
    private JLabel lblvs;
    private JLabel lblgreenhouse;
    private JLabel lblyellowhouse;
    private JLabel lblname;
    private JTextField txtbgreenentry;
    private JTextField txtbyellowentry;
    private JTextField txtbenterscoreg;
    private JTextField txtbenterscorey;
    private JButton btnfinalresults;
    private JScrollPane scrollpane;
    private JLabel lblcurrentscore;
    private JTextField txtbcurrentgs;
    private JTextField txtbcurrentys;
 
 
    public MyPanel()
    {
        //construct components
 
        btngenerate = new JButton("Generate Match List");
        txtbdisplaymatch = new JTextArea(5, 5);
        scrollpane = new javax.swing.JScrollPane(txtbdisplaymatch);
        scrollpane.setVerticalScrollBarPolicy(javax.swing.ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
        lblvs = new JLabel(" vs");
        lblgreenhouse = new JLabel(" Green House");
        lblyellowhouse = new JLabel(" Yellow House");
        lblname = new JLabel(" Name");
        txtbgreenentry = new JTextField(5);
        txtbyellowentry = new JTextField(5);
        txtbenterscoreg = new JTextField(5);
        txtbenterscorey = new JTextField(5);
        btnfinalresults = new JButton("Enter Match Score");
        lblcurrentscore = new JLabel ("Current Score");
        txtbcurrentgs = new JTextField (5);
        txtbcurrentys = new JTextField (5);
 
        //adjust size and set layout
        setPreferredSize(new Dimension(542, 542));
        setLayout(null);
 
        //add components
        add(btngenerate);
        add(scrollpane);
        add(lblvs);
        add(lblgreenhouse);
        add(lblyellowhouse);
        add(lblname);
        add(txtbgreenentry);
        add(txtbyellowentry);
        add(txtbenterscoreg);
        add(txtbenterscorey);
        add(btnfinalresults);
        add(lblcurrentscore);
        add(txtbcurrentgs);
        add(txtbcurrentys);
 
        //set component bounds (only needed by Absolute Positioning)
        btngenerate.setBounds(185, 25, 165, 20);
        scrollpane.setBounds(60, 70, 415, 320); /**Changed it from setting the bounds on the textarea to setting them on the scrollpane */
        lblvs.setBounds(285, 415, 25, 25);
        lblgreenhouse.setBounds(385, 415, 100, 25);
        lblyellowhouse.setBounds(120, 415, 100, 25);
        lblname.setBounds(30, 445, 45, 25);
        txtbgreenentry.setBounds(75, 445, 155, 20);
        txtbyellowentry.setBounds(355, 445, 155, 20);
        txtbenterscoreg.setBounds(235, 445, 20, 20);
        txtbenterscorey.setBounds(330, 445, 20, 20);
        btnfinalresults.setBounds(185, 495, 205, 25);
        lblcurrentscore.setBounds(245, 560, 205, 25);
        txtbcurrentgs.setBounds(150, 580, 25, 25);
        txtbcurrentys.setBounds(390, 580, 25, 25);
 
 
 
        //add action listener
        btngenerate.addActionListener(this);    //use the components name and use the ".addActionListener()" method to enable this component to take inputs
 
    }
 
    public void actionPerformed(ActionEvent e)
    {//create a method called actionPerformed, this method will contain the code which is run when the component is pressed.
 
        if (e.getSource() == btngenerate)
        { //use the getSource() method and use it to see if it is equal to the compoenent.
            txtbdisplaymatch.setText(ml.CreateMatch());  //use the setText() method to add text from variable a to the txtbdisplaymatch which will display in the text area when the generate button is pressed.
        }
    }
 
    public static void main(String[] args)
    {
        JFrame frame = new JFrame("MyPanel");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(new MyPanel());
        frame.pack();
        frame.setVisible(true);
    }
}