Thread: Testing double null

What do you want to test for? A primitive will never have a null value.

Perhaps the caller of the method could sort out what computation to do and call an appropriate method to solve it.

test whether or not a double is null

A primitive like double will never have a null value.

Originally Posted by Norm

A primitive like double will never have a null value.

Yes, I know that, as I mentioned in my first post. I'm not sure what you are suggesting I can do with the method to "sort out what computation to do".

Would this be attached to the calculate JButton some how?

test which JTextfields (variables) were left empty.

Test the String that is returned by the getText method.

user is actually just trying to to find acceleration.

Would the actionlistener know what the user wants to find and be able to see if the required data has been entered in some textfields? If any required data is missing, issue an error message and go back to the user for correction.

Where can a missing entry be detected? How can that information be passed to a method for processing?

If you passed wrapper class objects: Double vs double, the value could be null.

What info do you need to pass to the method? What are the ways to pass it?
If you use an object to pass a value to a method, then a value of null would show the data is missing.
Another way would be to use a variable to flag which of the other variables have no value. For example a boolean array with true/false values for which variables are defined and which are not defined.
callTheMethod(var1, var2, var3, boolArray);
boolArray would have 3 elements corresponding to var1, var2 and var3

cannot find symbol
symbol: method checkJTF(JTextField[])

The compiler can not find a definition for the method named in the error message. Where is that method define?
Is it in scope where the code tries to use it?

The code snippets don't show enough.

This is both classes in their entirety. Hopefully this will work. Thanks a lot for help.

package physicspractice;
 
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.*;
 
public class Frame extends JFrame{
 
    //Objects 
    final Kinematics kinematics = new Kinematics();
 
    public Frame() throws IOException {
		super("PhysAssist");
 
		// Buttons
		JButton kinematic = new JButton("Kinematic");
		kinematic.setMnemonic(KeyEvent.VK_K);
		JButton dynamics = new JButton("Dynamics");
		dynamics.setMnemonic(KeyEvent.VK_D);
		JButton power = new JButton("Power and Energy");
		power.setMnemonic(KeyEvent.VK_E);
		JButton wave = new JButton("Wave");
		wave.setMnemonic(KeyEvent.VK_W);
		JButton sound = new JButton("Sound");
		sound.setMnemonic(KeyEvent.VK_S);
		JButton circuit = new JButton("Circuit");
		circuit.setMnemonic(KeyEvent.VK_C);
 
		// Execute Buttons
		JButton calculate = new JButton("Calculate");
		calculate.setMnemonic(KeyEvent.VK_ENTER);
		calculate.setFont(new java.awt.Font("Georgia", Font.BOLD, 16));
		calculate.setForeground(Color.BLUE);
		JButton back = new JButton("Back");
		back.setMnemonic(KeyEvent.VK_ESCAPE);
		back.setFont(new java.awt.Font("Georgia", Font.ITALIC, 16));
		back.setForeground(Color.RED);
 
		// Button Array Characteristics
		final JButton[] buttonArray = { kinematic, dynamics, power, wave,
				sound, circuit };
		for (int i = 0; i < buttonArray.length; i++) {
			buttonArray[i].setFont(new java.awt.Font("Georgia", Font.BOLD, 16));
			buttonArray[i].setForeground(Color.darkGray);
			buttonArray[i].setBackground(Color.GRAY);
		}
 
		// Panels
		final JPanel mainPanel = new JPanel();
		mainPanel.setLayout(new BorderLayout());
 
		final JPanel executePanel = new JPanel();
		executePanel.setLayout(new FlowLayout());
		executePanel.add(back);
		executePanel.add(calculate);
 
		final JPanel sidePanel = new JPanel();
		sidePanel.setLayout(new BorderLayout());
 
		final JPanel buttonPanel = new JPanel();
		buttonPanel.setLayout(new GridLayout(6, 1));
		buttonPanel.setBackground(Color.DARK_GRAY);
 
		// Kinematic Pane and Contents
		final JPanel kinematicPane = new JPanel(new GridLayout(6, 2));
		kinematicPane.add(new JLabel("Initial Distance"));
		final JTextField dI = new JTextField();
		kinematicPane.add(dI);
		kinematicPane.add(new JLabel("Final Distance"));
		final JTextField d0 = new JTextField();
		kinematicPane.add(d0);
		kinematicPane.add(new JLabel("Initial Velocity"));
		final JTextField velocityI = new JTextField();
		kinematicPane.add(velocityI);
		kinematicPane.add(new JLabel("Final Velocity"));
		final JTextField velocityF = new JTextField();
		kinematicPane.add(velocityF);
		kinematicPane.add(new JLabel("Average Velocity"));
		final JTextField velocityAverage = new JTextField();
		kinematicPane.add(velocityAverage);
		kinematicPane.add(new JLabel("Acceleration"));
		final JTextField accelerationAverage = new JTextField();
		kinematicPane.add(accelerationAverage);
                final JTextField [] kinematicsJT = {dI, d0, velocityI, velocityF,
                velocityAverage, accelerationAverage};
 
 
 
		// Dynamics Pane
		final JPanel dynamicsPane = new JPanel(new GridLayout(6, 2));
		dynamicsPane.add(new JLabel("Force"));
		final JTextField force = new JTextField();
		dynamicsPane.add(force);
		dynamicsPane.add(new JLabel("Mass One"));
		final JTextField massOne = new JTextField();
		dynamicsPane.add(massOne);
		dynamicsPane.add(new JLabel("Mass One"));
		final JTextField massTwo = new JTextField();
		dynamicsPane.add(massTwo);
		dynamicsPane.add(new JLabel("Radius One"));
		final JTextField radiusOne = new JTextField();
		dynamicsPane.add(radiusOne);
		dynamicsPane.add(new JLabel("Radius Two"));
		final JTextField radiusTwo = new JTextField();
		dynamicsPane.add(radiusTwo);
		dynamicsPane.add(new JLabel("Normal Friction"));
		final JTextField frictionNormal = new JTextField();
		dynamicsPane.add(frictionNormal);
 
		// Power, Work, Energy Pane
		final JPanel powerPane = new JPanel(new GridLayout(7, 2));
		powerPane.add(new JLabel("Work"));
		final JTextField work = new JTextField();
		powerPane.add(work);
		powerPane.add(new JLabel("Energy"));
		final JTextField energy = new JTextField();
		powerPane.add(energy);
		powerPane.add(new JLabel("Power"));
		final JTextField powerP = new JTextField();
		powerPane.add(power);
		powerPane.add(new JLabel("Mass"));
		final JTextField mass = new JTextField();
		powerPane.add(mass);
		powerPane.add(new JLabel("Initial Time"));
		final JTextField timeOne = new JTextField();
		powerPane.add(timeOne);
		powerPane.add(new JLabel("Final Time"));
		final JTextField timeTwo = new JTextField();
		powerPane.add(timeTwo);
		powerPane.add(new JLabel("Velocity"));
		final JTextField velocity = new JTextField();
		powerPane.add(velocity);
		powerPane.add(new JLabel("Force"));
		final JTextField powerForce = new JTextField();
		powerPane.add(powerForce);
 
		final JPanel wavePane = new JPanel();
 
		final JPanel soundPane = new JPanel();
 
		final JPanel circuitPane = new JPanel(new GridLayout(3, 2));
		circuitPane.add(new JLabel("Voltage"));
		final JTextField voltage = new JTextField();
		circuitPane.add(voltage);
		circuitPane.add(new JLabel("Current"));
		final JTextField current = new JTextField();
		circuitPane.add(current);
		circuitPane.add(new JLabel("Resistance"));
		final JTextField resistance = new JTextField();
		circuitPane.add(resistance);
 
		// Add Header to JFrame
		/*final JPanel imagePanel = new JPanel();
		imagePanel.setBackground(Color.DARK_GRAY);
		BufferedImage bfimage = ImageIO.read(getClass().getResource(
				"physicsImg.jpg"));
		ImageLabel image = new ImageLabel(bfimage);
		JLabel headerLabel = new JLabel(new ImageIcon(bfimage));
		headerLabel.add(image);
		imagePanel.add(headerLabel);
                */
 
		// Add button components and header
 
		buttonPanel.add(kinematic);
		buttonPanel.add(dynamics);
		buttonPanel.add(power);
		buttonPanel.add(wave);
		buttonPanel.add(sound);
		buttonPanel.add(circuit);
 
		add(mainPanel);
		//mainPanel.add(imagePanel, BorderLayout.CENTER);
		mainPanel.add(buttonPanel, BorderLayout.SOUTH);
 
		validate();
 
		back.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent ae) {
				for (int i = 0; i < buttonArray.length; i++) {
					mainPanel.remove(buttonArray[i]);
				}
				mainPanel.remove(sidePanel);
				mainPanel.add(buttonPanel, BorderLayout.SOUTH);
				//mainPanel.add(imagePanel, BorderLayout.CENTER);
				mainPanel.revalidate();
				mainPanel.repaint();
			}
		});
 
		calculate.addActionListener(new ActionListener(){
			public void actionPerformed(ActionEvent ae){
			    kinematics.checkJTF(kinematicsJT);                                     
                            try{
				float distanceI = Float.parseFloat(dI.getText());
                                kinematics.setDistanceI(distanceI);
				float distanceF = Float.parseFloat(d0.getText());
				float v0 = Float.parseFloat(velocityI.getText());
				float v1 = Float.parseFloat(velocityF.getText());
				float vA = Float.parseFloat(velocityAverage.getText());
				float aA = Float.parseFloat(accelerationAverage.getText()); 
 
				} catch(NumberFormatException ex){
					JOptionPane.showConfirmDialog(null, "Numbers Only");
				}
			}
		});
 
		kinematic.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent ae) {
				sidePanel.add(kinematicPane, BorderLayout.CENTER);
				sidePanel.add(executePanel, BorderLayout.SOUTH);
				mainPanel.add(buttonPanel, BorderLayout.WEST);
				mainPanel.add(sidePanel, BorderLayout.CENTER);
				//mainPanel.remove(imagePanel);
				mainPanel.revalidate();
				mainPanel.repaint();		
			}
		});
 
		dynamics.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent ae) {
				sidePanel.add(dynamicsPane, BorderLayout.CENTER);
				sidePanel.add(executePanel, BorderLayout.SOUTH);
				mainPanel.add(sidePanel, BorderLayout.CENTER);
				mainPanel.add(buttonPanel, BorderLayout.WEST);
				//mainPanel.remove(imagePanel);
				mainPanel.revalidate();
				mainPanel.repaint();
 
				float f = Float.parseFloat(force.getText());
				float m1 = Float.parseFloat(massOne.getText());
				float m2 = Float.parseFloat(massTwo.getText());
				float r1 = Float.parseFloat(radiusOne.getText());
				float r2 = Float.parseFloat(radiusTwo.getText());
				float fN = Float.parseFloat(frictionNormal.getText());
			}
		});
 
		power.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent ae) {
				sidePanel.add(powerPane, BorderLayout.CENTER);
				sidePanel.add(executePanel, BorderLayout.SOUTH);
				mainPanel.add(sidePanel, BorderLayout.CENTER);
				mainPanel.add(buttonPanel, BorderLayout.WEST);
				//mainPanel.remove(imagePanel);
				mainPanel.revalidate();
				mainPanel.repaint();
 
				float w = Float.parseFloat(work.getText());
				float e = Float.parseFloat(energy.getText());
				float p = Float.parseFloat(powerP.getText());
				float m = Float.parseFloat(mass.getText());
				float t1 = Float.parseFloat(timeOne.getText());
				float t2 = Float.parseFloat(timeTwo.getText());
				float v = Float.parseFloat(velocity.getText());
				float pF = Float.parseFloat(powerForce.getText());
			}
		});
 
		wave.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent ae) {
				sidePanel.add(wavePane, BorderLayout.CENTER);
				sidePanel.add(executePanel, BorderLayout.SOUTH);
				mainPanel.add(sidePanel, BorderLayout.CENTER);
				mainPanel.add(buttonPanel, BorderLayout.WEST);
				//mainPanel.remove(imagePanel);
				mainPanel.revalidate();
				mainPanel.repaint();
			}
		});
 
		sound.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent ae) {
				sidePanel.add(soundPane, BorderLayout.CENTER);
				sidePanel.add(executePanel, BorderLayout.SOUTH);
				mainPanel.add(sidePanel, BorderLayout.CENTER);
				mainPanel.add(buttonPanel, BorderLayout.WEST);
				//mainPanel.remove(imagePanel);
				mainPanel.revalidate();
				mainPanel.repaint();
			}
		});
 
		circuit.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent ae) {
				sidePanel.add(circuitPane, BorderLayout.CENTER);
				sidePanel.add(executePanel, BorderLayout.SOUTH);
				mainPanel.add(sidePanel, BorderLayout.CENTER);
				mainPanel.add(buttonPanel, BorderLayout.WEST);
				//mainPanel.remove(imagePanel);
				mainPanel.revalidate();
				mainPanel.repaint();
 
				float volt = Float.parseFloat(voltage.getText());
				float cI = Float.parseFloat(current.getText());
				float rR = Float.parseFloat(resistance.getText());
			}
		});
 
    }
    public void checkJTF(JTextField[] a){
        for (int i = 0 ; i < a.length ; i++){
            if(a[i].getText().isEmpty()){
                int unknown = i;
                kinematics.setUnknown(unknown);
            }  
        }
    }
}

package physicspractice;
 
public class Kinematics {
 
    float distanceI, distanceF, velocityI, velocityF,
            velocityAverage, acceleration, timeF, timeI;
    int unknown;
 
    public Kinematics() {
        System.out.println(unknown);
        //float distance = distanceF - distanceI;
        //float time = timeF - timeI;
 
        if (unknown >= 0 && unknown <= 6) {
            switch (unknown) {
                case 1:
                    velocityF = velocityI + acceleration * (timeF - timeI);
                case 2:
                    distanceF = distanceI + ((velocityI + velocityF) / 2) * (timeF - timeI);
                case 3:
                    velocityF = (float) Math.sqrt(velocityI * velocityI) + 2 * acceleration * (distanceF - distanceI);
                case 4:
                    distanceF = (float) (velocityF * (timeF - timeI) + 0.5 * (acceleration * ((timeF - timeI) * (timeF - timeI))));
                case 5:
                    velocityAverage = (distanceF - distanceI) / (timeF - timeI);
            }
        }
    }
 
    public void setDistanceI(float distanceI) {
        this.distanceI = distanceI;
    }
 
    public void setDistanceF(float distanceF) {
        this.distanceF = distanceF;
    }
 
    public void setVelocityI(float velocityI) {
        this.velocityI = velocityI;
    }
 
    public void setVelocityF(float velocityF) {
        this.velocityF = velocityF;
    }
 
    public void setVelocityAverage(float velocityAverage) {
        this.velocityAverage = velocityAverage;
    }
 
    public void setAcceleration(float acceleration) {
        this.acceleration = acceleration;
    }
 
    public void setUnknown(int unknown) {
        this.unknown = unknown;
    }
 
    public int getUnknown() {
        return unknown;
    }
 
    public double getDistanceI() {
        return distanceI;
    }
 
    public double getDistanceF() {
        return distanceF;
    }
 
    public double getVelocityI() {
        return velocityI;
    }
 
    public double getVelocityF() {
        return velocityF;
    }
 
    public double getVelocityAverage() {
        return velocityAverage;
    }
 
    public double getAcceleration() {
        return acceleration;
    }
}

I can not compile the post code without many compiler errors.
Most are due to missing import statements.

Can you make a small, complete program that shows the error. Not 30+ errors

See post#18

NOTE: Frame is the name of a Java SE class. It's better not to use names that conflict with Java SE class names.

fix the simple issue with the method by adding the static

That doesn't make sense with the code in post#19

it will not pass the value to the kinematics class.

Can you explain where the code is trying to pass a value to that class?