Text area exceeds the window area

I have wrote program in java the program is to convert from KM to miles and miles to KM the program works fine but the problem is in the result in text area exceeded the area so does not appear the full text below the code attached. so i want if it is reached at the end of line it goes to new line

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Converter extends JFrame implements ActionListener {
JLabel label = new JLabel("Distance : ");
JTextField input = new JTextField(10);
JButton button = new JButton("Convert");
JTextArea output = new JTextArea(10,15);
CheckboxGroup cbg = new CheckboxGroup();
Checkbox cb1 = new Checkbox("Convert MILES to KM", cbg, true);
Checkbox cb2 = new Checkbox("Convert KM to MILES", cbg, false);
public static void main(String args[]) {
Converter s = new Converter();
s.setVisible(true);
}
public Converter() {
setLayout(null);
setSize(300,400);  
//left-down-width-hegiht
cb1.setBounds(60,30,150,30);
cb2.setBounds(60,60,150,30);
label.setBounds(30,90,120,30);
input.setBounds(90,95,170,20);
button.setBounds(100,130,90,30);
output.setBounds(45,168,200,165);	
add(cb1);
add(cb2);
add(label);
add(input);
add(button);
add(output);
button.addActionListener(this);
}
public void actionPerformed(ActionEvent e) {
if (cb1.getState() ) {
if (e.getSource() == button) {
double d = Double.parseDouble(input.getText());
double d2 =  d / 0.62;
String str2 = String.valueOf(d2); 
output.setText(d + "miles equals to " + str2 + " kilometers");		
}		
}
if (cb2.getState()) {
if (e.getSource() == button){
double d = Double.parseDouble(input.getText());
double d2 =  d * 0.62;
String str2 = String.valueOf(d2);
output.setText(d + " kilometers equals to " + str2 + " miles ");
}			
}	
}		 
}

If your goal is purely to have line wrapping on in the text area then you can make use of JTextArea's built-in function named setLineWrap.

Passing a true boolean value as a parameter to setLineWrap such as setLineWrap(true) will turn on line wrapping for the JTextArea component. Passing a false boolean value as a parameter will turn off line wrapping

In your code, it would be used as follows.

output.setLineWrap(true);

The Converter constructor will then look as follows.

	public Converter() {
// Turn on line wrapping.
output.setLineWrap(true);
setLayout(null);
setSize(300, 400);
// left-down-width-hegiht
cb1.setBounds(60, 30, 150, 30);
cb2.setBounds(60, 60, 150, 30);
label.setBounds(30, 90, 120, 30);
input.setBounds(90, 95, 170, 20);
button.setBounds(100, 130, 90, 30);
output.setBounds(45, 168, 200, 165);
add(cb1);
add(cb2);
add(label);
add(input);
add(button);
add(output);
button.addActionListener(this);
}