Okay, so I tried making the program with this coding:

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.util.*;
import java.io.*;
import java.text.SimpleDateFormat;


public class SwimmCalc extends JFrame implements ActionListener{
private JTabbedPane jtabbedPane;
private JPanel general;
private JPanel pools;
private JPanel hotTubs;
private JPanel tempCalc;
private JPanel customers;
private JPanel options;
private JComponent date;
JTextField lengthText, widthText, depthText, volumeText;

public MainPool(){
setTitle( "Pools," );
setSize( 300, 200 );
setBackground( Color.blue);

JPanel topPanel = new JPanel();
topPanel.setLayout( new BorderLayout() );
getContentPane().add( topPanel );

createGeneral();
createPools();
createHotTubs();
createTempCalc();
createCustomers();
createOptions();

jtabbedPane = new JTabbedPane();
jtabbedPane.addTab( "General", general );
jtabbedPane.addTab( "Pools", pools );
jtabbedPane.addTab( "Hot Tubs", hotTubs );
jtabbedPane.addTab( "Temp Calculator", tempCalc );
jtabbedPane.addTab( "Customers", customers );
jtabbedPane.addTab( "Options", options );

topPanel.add(jtabbedPane, BorderLayout.CENTER );
}
public void createGeneral(){
general = new JPanel();
general.setLayout( null );

JLabel dateLabel = new JLabel( "Todays Date" );
dateLabel.setBounds( 10, 15, 150, 20 );
general.add( dateLabel );

JFormattedTextField date = new JFormattedTextField(
java.util.Calendar.getInstance().getTime());
date.setEditable(false);
date.setBounds(150,15,150,20);
general.add(date);

JButton quit = new JButton("Quit");
quit.setBounds(10,80,150,30);
quit.addActionListener(this);
quit.setBackground(Color.red);
general.add(quit);
}
public void createPools(){
pools = new JPanel();
pools.setLayout( null );

JLabel lengthLabel = new JLabel( "Enter the length of swimming pool(ft):" );
lengthLabel.setBounds( 10, 15, 260, 20 );
pools.add( lengthLabel );

lengthText = new JTextField();
lengthText.setBounds( 260, 15, 150, 20 );
pools.add( lengthText );

JLabel widthLabel = new JLabel( "Enter the width of the swimming pool(ft):" );
widthLabel.setBounds( 10, 60, 260, 20 );
pools.add( widthLabel );

widthText = new JTextField();
widthText.setBounds( 260, 60, 150, 20 );
pools.add( widthText );

JLabel depthLabel = new JLabel( "Enter the average depth the swimming pool(ft):" );
depthLabel.setBounds( 10, 100, 260, 20 );
pools.add( depthLabel );

depthText = new JTextField();
depthText.setBounds( 260, 100, 150, 20 );
pools.add( depthText );

JLabel volumeLabel = new JLabel( "The pool volume is:(ft ^3" );
volumeLabel.setBounds( 10, 200, 260, 20 );
pools.add( volumeLabel );

volumeText = new JTextField();
volumeText.setBounds( 260, 200, 150, 20 );
volumeText.setEditable(false);
pools.add( volumeText );
JButton calcVolume = new JButton("Calculate Volume");
calcVolume.setBounds(150,250,150,30);
calcVolume.addActionListener(this);
calcVolume.setBackground(Color.yellow);
pools.add(calcVolume);

JButton quit = new JButton("Quit");
quit.setBounds(350,250,80,30);
quit.addActionListener(this);
quit.setBackground(Color.red);
pools.add(quit);
}
public void createHotTubs(){
hotTubs = new JPanel();
hotTubs.setLayout( new GridLayout( 3, 2 ) );
hotTubs.add( new JLabel( "Field 1:" ) );
hotTubs.add( new TextArea() );
hotTubs.add( new JLabel( "Field 2:" ) );
hotTubs.add( new TextArea() );
hotTubs.add( new JLabel( "Field 3:" ) );
hotTubs.add( new TextArea() );
}
public void createTempCalc(){
tempCalc = new JPanel();
tempCalc.setLayout( null );
JLabel tempLabel = new JLabel( "Enter temperature:" );
tempLabel.setBounds( 10, 15, 260, 20 );
tempCalc.add( tempLabel );

JTextField temp = new JTextField();
temp.setBounds( 260, 15, 150, 20 );
tempCalc.add( temp );

JLabel resultsLabel = new JLabel( "Calculated Temp:" );
resultsLabel.setBounds( 10, 60, 260, 20 );
tempCalc.add( resultsLabel );

JTextField results = new JTextField();
results.setBounds( 260, 60, 150, 20 );
results.setEditable(false);
tempCalc.add( results );

JButton calcVol = new JButton("Calculate Volume");
calcVol.setBounds(100,115,150,30);
calcVol.addActionListener(this);
calcVol.setBackground(Color.yellow);
tempCalc.add(calcVol);

JButton quit = new JButton("Quit");
quit.setBounds(250,115,80,30);
quit.addActionListener(this);
quit.setBackground(Color.red);
tempCalc.add(quit);
}
public void createCustomers(){}
public void createOptions()
{
options = new JPanel();
options.setLayout( null );
JLabel labelOptions = new JLabel( "Change Company Name:" );
labelOptions.setBounds( 150, 50, 150, 20 );
options.add( labelOptions );

JTextField newTitle = new JTextField();
newTitle.setBounds( 150, 70, 150, 20 );
options.add( newTitle );

JButton newName = new JButton("Set New Name");
newName.setBounds(100,115,150,30);
newName.addActionListener(this);
newName.setBackground(Color.yellow);
options.add(newName);

JButton quit = new JButton("Quit");
quit.setBounds(250,115,80,30);
quit.addActionListener(this);
quit.setBackground(Color.red);
options.add(quit);
}
public void actionPerformed(ActionEvent event){
JButton button = (JButton)event.getSource();
String buttonLabel = button.getText();
if ("Quit".equalsIgnoreCase(buttonLabel)){
Exit_pressed(); return;
}
if ("Set New Name".equalsIgnoreCase(buttonLabel)){
New_Name(); return;
}
if ("Calculate Volume".equalsIgnoreCase(buttonLabel)){
Calculate_Volume(); return;
}
if ("Customers".equalsIgnoreCase(buttonLabel)){
Customers(); return;
}
if ("Calculate Volume".equalsIgnoreCase(buttonLabel)){
Calculate_Volume(); return;
}
if ("Options".equalsIgnoreCase(buttonLabel)){
Options(); return;
}
}
private void Exit_pressed(){
System.exit(0);
}
private void New_Name(){
System.exit(0);
}
private void Calculate_Volume(){
String lengthString, widthString, depthString;
int length=0;
int width=0;
int depth=0;

lengthString = lengthText.getText();
widthString = widthText.getText();
depthString = depthText.getText();
if ( lengthString.length() < 1 || widthString.length() < 1 || depthString.length() < 1 ){
volumeText.setText( "Error! Must enter in all three numbers!!" ); return;
}
length = Integer.parseInt(lengthString );
width = Integer.parseInt(widthString );
depth = Integer.parseInt(depthString);
if ( length != 0 || width != 0 || depth != 0 ){
volumeText.setText((length * width * depth) + "" );
} else{
volumeText.setText( "Error! Must Enter in all three numbers!!" ); return;
}
}
private void Customers(){}
private void Options(){}
public static void main(String[] args){
JFrame frame = new MainPool();
frame.setSize(525, 350);
frame.setVisible(true);
}

}


However there is an error at line 20 saying the return type is missing?? Any help please?!?!