Ufdjrw

Seems like the only option is to set number of rows, but I need my text area to be resizable for user.
JScrollPane helps, but when there's a lot of text, I want to let user resize the area itself.

How do I do this? If I can use another class for this purpose, I'll be totally ok with it.

Simplified code is

import javax.swing.*;
import java.awt.*;

public class Problematic 

 public static void main(String[] args) 
 JFrame f = new JFrame("frame");
 f.setLayout(new BorderLayout());

 JPanel p1 = new JPanel();
 JPanel p = new JPanel();

 JButton button = new JButton("Whatever here");
 JTextArea t2 = new JTextArea(5, 30);

 JScrollPane scrollPane = new JScrollPane(t2);

 scrollPane.setSize(600, 400);
 scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

 t2.setText("this is some random textnthat may go for many rowsnso it may look messy");

 p1.add(button);
 p.add(scrollPane);

 f.add(p, BorderLayout.NORTH);
 f.add(p1, BorderLayout.CENTER);

 f.setSize(600, 500);
 f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
 f.setVisible(true);
 

As first improvement you can make some small layout changes that will make the JTextArea occupy the whole space and resize with the frame :

import java.awt.BorderLayout;
import java.awt.GridLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.WindowConstants;

public class Problematic 

 public static void main(String[] args) 
 JFrame f = new JFrame("frame");
 f.setLayout(new BorderLayout()); 

 JPanel p = new JPanel(new GridLayout(1, 1)); //assign gridlayout so text area fills panel 
 JTextArea t2 = new JTextArea(5, 30);
 t2.setText("this is some random textnthat may go for many rowsnso it may look messy");

 JScrollPane scrollPane = new JScrollPane(t2);
 scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
 p.add(scrollPane);
 f.add(p, BorderLayout.CENTER); //place text area panel in center position 

 JPanel p1 = new JPanel();
 JButton button = new JButton("Whatever here");
 p1.add(button);
 f.add(p1, BorderLayout.PAGE_END);

 f.setSize(600, 500);
 f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
 f.setVisible(true);
 

for additional flexibility you can add a JSplitPane :

public class Problematic 

 public static void main(String[] args) 
 JFrame f = new JFrame("frame");
 f.getContentPane().setLayout(new BorderLayout());

 JPanel p1 = new JPanel();
 JButton button = new JButton("Whatever here");
 p1.add(button);

 JPanel p = new JPanel(new GridLayout(1, 1)); //assign gridlayout so text area fills panel
 JTextArea t2 = new JTextArea(5, 30);
 t2.setText("this is some random textnthat may go for many rowsnso it may look messy");

 JScrollPane scrollPane = new JScrollPane(t2); scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
 p.add(scrollPane);

 JSplitPane splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT, p,p1);
 f.getContentPane().add(splitPane, BorderLayout.CENTER);

 f.setSize(600, 500);
 f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
 f.setVisible(true);
 

You can use JSplitPane to make various areas of a window resizable. Try below example. See my comments in the code as well.

import javax.swing.*;
import java.awt.*;

public class Problematic 

 public static void main(String[] args) 
 JFrame f = new JFrame("frame");
 f.setLayout(new BorderLayout());

 JPanel p1 = new JPanel();
 JPanel p = new JPanel();
 // Set BorderLayout so that scroll pane fills the panel
 p.setLayout(new BorderLayout());

 JButton button = new JButton("Whatever here");
 JTextArea t2 = new JTextArea(5, 30);

 JScrollPane scrollPane = new JScrollPane(t2);

 // Setting scroll pane size is not necessary
 //scrollPane.setSize(600, 400);
 scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

 t2.setText("this is some random textnthat may go for many rowsnso it may look messy");

 p1.add(button);
 p.add(scrollPane);

 // Use JSplitPane to make the panels resizable
 f.add(new JSplitPane(JSplitPane.VERTICAL_SPLIT, p, p1), BorderLayout.CENTER);

 f.setSize(600, 500);
 f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
 f.setVisible(true);
 

Here is c0der's implementation, but set-up for a more streamlined life-cycle. Each block of lines explains what is going on and when.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.text.JTextComponent;

public class TextApp implements Runnable 
 private static final String APP_NAME = "Text App";

 private JFrame frame;
 private JTextArea txtAra;
 private JButton button;

 // This is a generic action that handles clearing the text of a JTextComponent
 // It can also be a stand-alone class
 private static class ClearAction <T extends JTextComponent> implements ActionListener 
 private T txtAra;

 public ClearAction(T txtAra) 
 this.txtAra = txtAra;
 

 @Override
 public void actionPerformed(ActionEvent e) 
 this.txtAra.setText("");
 
 

 public TextApp() 
 // Initialize instance fields
 frame = new JFrame(APP_NAME);
 txtAra = new JTextArea(5, 30);
 button = new JButton("Clear Text");

 // Internal panels used for layout
 JPanel mainPanel = new JPanel(new GridLayout(1, 1));
 JScrollPane scrollPane = new JScrollPane(txtAra);
 JPanel buttonPanel = new JPanel();

 // Add components to containers
 frame.setLayout(new BorderLayout());
 frame.add(mainPanel, BorderLayout.CENTER);
 frame.add(buttonPanel, BorderLayout.PAGE_END);
 mainPanel.add(scrollPane);
 buttonPanel.add(button);

 // Additional setup
 scrollPane.setSize(600, 400);
 scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

 // Add listeners
 button.addActionListener(new ClearAction(txtAra));
 

 @Override
 public void run() 
 // Set text
 txtAra.setText("this is some random textnthat may go for many rowsnso it may look messy");

 // Prepare frame
 frame.pack();
 frame.setLocationRelativeTo(null);
 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 frame.setVisible(true);
 

 public static void main(String[] args) 
 SwingUtilities.invokeLater(new TextApp());