Thread: drawString

When you get errors, it helps us solve the problem if you post all of the text of the error message here.

ok i added the error it get

Now you need to learn to read the stack trace.
Look at these lines starting at the bottom:

PHP Code:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at Algebra.Functions.twostep.math(twostep.java:17)  << at line 17 there is a null variable !!!!
    at Algebra.getInput.Equations(getInput.java:23)   << Equations calls getInput at line 23 
    at Algebra.GUI.actionPerformed(GUI.java:74)   <<<<<<<<< GUI line 23 calls Equations 


What is the variable with the null value at line 17 in twostep?
When you find the variable, trace back thru your code to see why that variable does not have a value.

that variable is defined by the user it has a value but for some reason drawString isnt recognizing it

Defining a variable does not give it a value (except for primitives).
What variable is null?
Where does your code assign a value to the variable.

drawString isnt recognizing it

drawString is a method of the Graphics class. Is one of its arguments null? If that were true, the error message that you posted would show that you had called the drawString method and that the error occurred in the drawString method's code.

would this be causing the problem?

twostep.math(null);

that is in the getInput class

yes it would if the variable twostep is null. Or if the math() method expects to receive a value other than null.

so what would need to go in place of that?

To get a graphics object, use the one passed to the paintComponent() method. Call the math() method from paintComponent() and use the Graphics object it receives as math()'s argument.

ok so in paintComponet i called twostep.math(g)

	public void paintComponet(Graphics2D g) {
		super.paintComponent(g);
		twostep.math(g);
	}

in getInput i was still having a problem with. it sayed:

Graphics2D cannot be resolved	AlgebraCalculator/src/Algebra	getInput.java	line 26

i used one of the quick fix options (im using eclipse) and it says create a field for Grafics2D

witch is

private static Graphics2D Graphics2D;

heres my getInput class

package Algebra;
 
import java.awt.Graphics2D;
 
import javax.swing.JOptionPane;
import Algebra.Functions.*;
 
public class getInput {
 
 
	private static Graphics2D Graphics2D;
	public static void Equations() {
	int size = 0;
		while (size < 1) {
			String Choose = JOptionPane
					.showInputDialog("One or Two Step Equation?");
			size = Integer.parseInt(Choose);
			System.out.println("Your Equation will be a " + size
					+ " Step Equation!");
 
			if (size == 1) {
				onestep.math();
			}
 
			if (size == 2) {
				twostep.math(Graphics2D);
			}
 
			if ((size > 2) || (size < 1)) {
				System.out.println("I'm sorry but equation size " + size
						+ " is not currently compatible!");
				size = 0;
			}
		}
	}
	public static void Area() {
		int shape = 0;
		String Choose = JOptionPane
			.showInputDialog("One or Two Step Equation?");
		shape = Integer.parseInt(Choose);
 
		if (shape == 1) {
			area.Rectangle();
		}
	}
 
}

it still crashes how ever and here is the there

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
	at Algebra.Functions.twostep.math(twostep.java:17)
	at Algebra.getInput.Equations(getInput.java:26)
	at Algebra.GUI.actionPerformed(GUI.java:74)
	at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
	at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
	at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
	at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
	at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
	at java.awt.Component.processMouseEvent(Unknown Source)
	at javax.swing.JComponent.processMouseEvent(Unknown Source)
	at java.awt.Component.processEvent(Unknown Source)
	at java.awt.Container.processEvent(Unknown Source)
	at java.awt.Component.dispatchEventImpl(Unknown Source)
	at java.awt.Container.dispatchEventImpl(Unknown Source)
	at java.awt.Component.dispatchEvent(Unknown Source)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
	at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
	at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
	at java.awt.Container.dispatchEventImpl(Unknown Source)
	at java.awt.Window.dispatchEventImpl(Unknown Source)
	at java.awt.Component.dispatchEvent(Unknown Source)
	at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
	at java.awt.EventQueue.access$000(Unknown Source)
	at java.awt.EventQueue$1.run(Unknown Source)
	at java.awt.EventQueue$1.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
	at java.awt.EventQueue$2.run(Unknown Source)
	at java.awt.EventQueue$2.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
	at java.awt.EventQueue.dispatchEvent(Unknown Source)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.run(Unknown Source)

Graphics2D cannot be resolved

Do you have the correct import statement?

im importing
import java.awt.Graphics2D;

into getInput wich is correct

At this point, you need to post code that compiles and executes and demonstrates the problem.
I can't make sense out of all the bits and pieces you've been posting. I need to see a complete program that demonstrates the problem.

To get the graphics object, you need to be in the paintComponent class and call the methods that will do the drawing from there. Pass them the graphics object passed to the paintComponent method.

ok heres all the classes involved:

getInput:

package Algebra;
 
import java.awt.Graphics2D;
 
import javax.swing.JOptionPane;
import Algebra.Functions.*;
 
public class getInput {
 
 
	private static Graphics2D Graphics2D;
	public static void Equations() {
	int size = 0;
		while (size < 1) {
			String Choose = JOptionPane
					.showInputDialog("One or Two Step Equation?");
			size = Integer.parseInt(Choose);
			System.out.println("Your Equation will be a " + size
					+ " Step Equation!");
 
			if (size == 1) {
				onestep.math();
			}
 
			if (size == 2) {
				twostep.math(Graphics2D);
			}
 
			if ((size > 2) || (size < 1)) {
				System.out.println("I'm sorry but equation size " + size
						+ " is not currently compatible!");
				size = 0;
			}
		}
	}
	public static void Area() {
		int shape = 0;
		String Choose = JOptionPane
			.showInputDialog("One or Two Step Equation?");
		shape = Integer.parseInt(Choose);
 
		if (shape == 1) {
			area.Rectangle();
		}
	}
 
}

Painting:

package Algebra;
 
import java.awt.*;
import javax.swing.*;
import Algebra.Functions.*;
 
@SuppressWarnings("serial")
public class Painting extends JPanel {
 
	public Painting() {
		setBackground(Color.CYAN);
	}
 
	public void paintComponet(Graphics2D g) {
		super.paintComponent(g);
		twostep.math(g);
	}
}

twostep:

package Algebra.Functions;
 
import javax.swing.JOptionPane;
import java.text.DecimalFormat;
import java.awt.*;
 
import Algebra.getInput;
 
public class twostep {
 
	public static void math(Graphics2D Graphics2D) {
		Graphics2D g = (Graphics2D);
		DecimalFormat f = new DecimalFormat("#########.#########");
			String First = JOptionPane.showInputDialog("Enter your Constant.");
			Variables.nonCoef = Double.parseDouble(First);
			System.out.println("[Set Up] You Entered: "+f.format(Variables.nonCoef));
			g.drawString("[Set Up] You Entered: "+f.format(Variables.nonCoef)+"", 1, 1);
 
			String Second = JOptionPane.showInputDialog("Enter Your Coeficiant.");
			Variables.coeficiant = Double.parseDouble(Second);
			System.out.println("[Set Up] You Entered: "+f.format(Variables.coeficiant));
 
			String Third  = JOptionPane.showInputDialog("Enter Number right of =");
			Variables.equationEquals = Double.parseDouble(Third);
			System.out.println("[Set Up] You Entered: "+f.format(Variables.equationEquals));
 
			Variables.fstans = ((double) (Variables.equationEquals - Variables.nonCoef));
			Variables.xeqls = ((double) (Variables.fstans / Variables.coeficiant));
 
			System.out.println("....................................");
			System.out.println("[Set Up] Your Equation is: "+f.format(Variables.nonCoef)+"+"+f.format(Variables.coeficiant)+"x="+f.format(Variables.equationEquals));
			System.out.println("....................................");
			System.out.println("[Step 1] "+f.format(Variables.equationEquals)+"-"+f.format(Variables.nonCoef));
			System.out.println("[Step 1 Explanation] Subtract the nonCoefber with no varible from...");
			System.out.println("...the nonCoefber on right of equal sing, and remove.");
			System.out.println("....................................");
			System.out.println("[Equation] "+f.format(Variables.coeficiant)+"x="+f.format(Variables.fstans));
			System.out.println("[Step 2] "+f.format(Variables.fstans)+"/"+f.format(Variables.coeficiant));
			System.out.println("[Step 2 Explanation] Devide the nonCoef. to the right of = by the coefitant...");
			System.out.println("...what remains is the vaule of your variable!");
			System.out.println("....................................");
			System.out.println("[Awnser] x = "+f.format(Variables.xeqls));
			getInput.Equations();
	}
 
}

and GUI:

package Algebra;
 
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
 
import Algebra.getInput;
 
public class GUI implements ActionListener {
 
	// Create Frame
	private JFrame f = new JFrame("Joshs' Algebra Calculator");
 
	// Create Panels
	private JPanel funcPnl = new JPanel();
	//private JTextField txtNotes = new JTextField();
 
	// Buttons
	private JButton algButton = new JButton("Equations");
	private JButton areaButton = new JButton("Area");
 
	// Create Menu
	private JMenuBar mb = new JMenuBar();
	private JMenu muFile = new JMenu("File");
	private JMenuItem muItemQuite = new JMenuItem("Quit");
	private JMenu muHelp = new JMenu("Help");
	private JMenuItem muItemAbout = new JMenuItem("About");
 
	public GUI() {
		// set menu
		f.setJMenuBar(mb);
 
		// build menu
		muFile.add(muItemQuite);
		muHelp.add(muItemAbout);
		mb.add(muFile);
		mb.add(muHelp);
 
		// Add Buttons
		funcPnl.add(algButton);
		funcPnl.add(areaButton);
 
		// Set Up Frame
 
		f.setSize(400, 300);
		f.getContentPane().setLayout(new BorderLayout());
		f.getContentPane().add(funcPnl, BorderLayout.WEST);
		//f.getContentPane().add(txtNotes, BorderLayout.SOUTH);
 
		// Allows the Swing App to be closed
		f.addWindowListener(new ListenCloseWdw());
 
		// Add Menu & Button listener
		muItemQuite.addActionListener(new ListenMenuQuit());
		muItemAbout.addActionListener(this);
		algButton.addActionListener(this);
		areaButton.addActionListener(this);
 
		// Buttons
		muItemAbout.setActionCommand("About");
		algButton.setActionCommand("Algebra");
		areaButton.setActionCommand("Area");
	}
 
	@Override
	public void actionPerformed(ActionEvent e) {
		String cmd = e.getActionCommand();
		if (cmd != null) {
			if (cmd.equalsIgnoreCase("About")) {
				JOptionPane.showMessageDialog(f,
						"This Software is made by Josh Artuso");
			}
			if (cmd.equalsIgnoreCase("Algebra")) {
				getInput.Equations();
			}
			if (cmd.equalsIgnoreCase("Area")) {
				getInput.Area();
			}
		}
	}
 
	public class ListenMenuQuit implements ActionListener {
		public void actionPerformed(ActionEvent e) {
			System.exit(0);
		}
	}
 
	public class ListenCloseWdw extends WindowAdapter {
		public void windowClosing(WindowEvent e) {
			System.exit(0);
		}
	}
 
	public void launchFrame() {
		// Display Frame
		Painting panel = new Painting();
		Container pane = f.getContentPane();
		pane.setLayout(new GridLayout (1,1));
		pane.add(panel);
		f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		f.setVisible(true);
		f.setResizable(false);
		f.setIconImage(Toolkit.getDefaultToolkit().getImage("favicon.gif"));
	}
 
	public static void main(String args[]) {
		GUI gui = new GUI();
		gui.launchFrame();
	}
}

GUI is the main class

Try to make a small simple program that compiles and executes to display the problem.
Don't bother to post more of this large, multi part code.
It needs to demonstrate only what the problem is. The rest is just in the way.