Thread: JFrames not coming up?

Ok, so I've had my three classes, and nothing seems to be running for me. It compiles well, just my swing components don't appear.

Here's the code:
GUI Class

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.Random;
 
public class StudentGUI extends JFrame
	implements ActionListener
	{
		static JButton[] action;
		static JFrame[] frame;
		static JPanel[] panel;
		static JTextArea[] area;
 
		public StudentGUI()
		{
			super("StudentGrades.java");
			action = new JButton[10];
			action[0] = new JButton("Construct");
			action[0].addActionListener(this);
			action[0].setMnemonic(KeyEvent.VK_C);
 
			for(int i = 1; i < action.length; i++)
			{
				action[i] = new JButton("Action " + i);
				action[i].addActionListener(this);
			}
			area = new JTextArea[8];
			for(int i = 0; i < area.length; i++)
			{
				area[i] = new JTextArea();
				area[i].setLineWrap(true);
				area[i].setEditable(false);
			}
			Container c = getContentPane();
			JPanel buttonPanel = new JPanel(new FlowLayout());
			for(int i = 0; i < action.length; i++)
			{
				buttonPanel.add(action[i]);
			}
			c.setBackground(Color.white);
			c.add(buttonPanel, BorderLayout.CENTER);
			panel = new JPanel[9];
			for(int i = 0; i < panel.length;)
			{
				panel[i] = new JPanel(new FlowLayout());
			}
 
 
			frame  = new JFrame[9];
			for(int i = 0; i < frame.length; i++)
			{
				frame[i] = new JFrame("Action Window");
				frame[i].getContentPane();
				frame[i].setBounds(300,300,100,100);
				frame[i].setResizable(true);
				frame[i].setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
				frame[1].setVisible(true);
			}
			for(int i = 0; i < panel.length; i++)
			{
				panel[i].add(area[i]);
				frame[i].add(panel[i], BorderLayout.CENTER);
			}
 
		}
		public void actionPerformed(ActionEvent e)
		{
			JButton button = (JButton)e.getSource();
			Random r = new Random();
			StudentGrades sg = null;
			int[] scores = null;
			int[] sorted = null;
 
			if(button == action[0])
			{
				sg = new StudentGrades(r.nextInt(21)+1);
			}
			if(button == action[1])
			{
				scores = sg.getTestGrades();
				frame[0].setVisible(true);
				for(int i = 0; i < scores.length; i++)
				{
					area[0].append(scores[i] + " ");
				}
 
			}
			if(button == action[2])
			{
				frame[0].setVisible(false);
				sorted = sg.selectionSortB(scores);
				frame[1].setVisible(true);
					for(int i = 0; i < sorted.length; i++)
				{
					area[1].append(sorted[i] + " ");
				}
 
			}
			/*if(button == action[3])
			{	frane[1].setVisible(false);
				frame[2].setVisible(true);
				area[2].append("The array is " + sg.isEqual(sorted));
			}*/
			if(button == action[4])
			{
				frame[2].setVisible(false);
				frame[3].setVisible(true);
				int highest = sg.highestGrade(sorted);
				area[3].append("The Highest grade is " + highest);
			}
			if(button == action[5])
			{
				frame[3].setVisible(false);
				frame[4].setVisible(true);
				int lowest = sg.lowestGrade(sorted);
				area[4].append("The Lowest grade is " + lowest);
			}
			if(button == action[6])
			{
				frame[4].setVisible(false);
				frame[5].setVisible(true);
				double average = sg.averageGrade(sorted);
				area[5].append("The average grade is " + average);
			}
			if(button == action[7])
			{
				frame[5].setVisible(false);
				frame[6].setVisible(true);
				int median = sg.medianGrade(sorted);
				area[6].append("The median grade is " + median);
			}
			if(button == action[8])
			{
				frame[6].setVisible(false);
				frame[7].setVisible(true);
				int mode = sg.modeGrade(sorted);
				area[7].append("The mode is " + mode);
			}
		}
	}

Method class

import java.util.Random;
public class StudentGrades
{
	private int[] studentGrades;
	public StudentGrades(int students)
	{
		Random r = new Random();
		studentGrades = new int[students];
		for(int i = 0; i < studentGrades.length; i++)
		{
			studentGrades[i] = r.nextInt(101);
		}
 
	}
	public int[] getTestGrades()
	{
		int[] testGrades = new int[studentGrades.length];
		for(int i = 0; i < studentGrades.length; i++)
		{
			testGrades[i]= studentGrades[i];
		}
		return testGrades;
	}
	public int[] selectionSortB(int[] nums)
   {
   		int size = nums.length;
      //  Same as version A, but sorts in ascending order
 
      int first, current, least, temp;
 
      for(first = 0; first < size; first = first + 1)
      {
         least = first;
         for(current = first+1; current < size; current = current + 1)
         {  if (nums[current] < nums[least])
            {  least = current; }
         }
         temp = nums[least];
         nums[least] = nums[first];
         nums[first] = temp;
      }
      return nums;
   }
   /*public boolean isEqual(int[] arr)
   {
   }*/
   public int highestGrade(int[] arr)
   {
   		int max = 0;
   		for(int i = 0; i < arr.length; i++)
   		{
   			if(arr[i] > max)
   			{
   				max = arr[i];
   			}
 
   		}
   		return max;
   }
   public int lowestGrade(int[] arr)
   {
   		int min = arr[0];
   		for(int i = 1; i < arr.length; i++)
   		{
   			if(arr[i] < min)
   				min = arr[i];
 
   		}
   		return min;
   }
   public double averageGrade(int[] arr)
   {
   		double total = 0.0;
   		for(int i = 0; i < arr.length; i++)
   		{
   			total += (double)arr[i];
   		}
   		double avg = total / arr.length;
   		return avg;
   }
   public int medianGrade(int[] arr)
   {
   		int median = (arr[0] + arr[arr.length - 1]) / 2 ;
   		return median;
   }
   public int modeGrade(int[] arr)
   {
   		int[] count = new int[arr.length];
   		for(int i = 0; i < arr.length; i++)
   		{
   			count[i]++;
   		}
   		int max = 0;
   		for(int i = 0; i < count.length; i++)
   		{
   			if(count[i] > max)
   			{
   				max  = count[i];
   			}
   		}
   		return count[max];
 
   }
 
}

Client class

public class Student
{
	public static void main(String[] args)
	{
 
		StudentGUI sgu = new StudentGUI();
		sgu.setBounds(400,400,100,100);
		sgu.setVisible(true);
		sgu.setDefaultCloseOperation(sgu.EXIT_ON_CLOSE);
		sgu.setResizable(true);
 
 
	}
}

Thanks for the help.

I believe you have to set the components to be visible too with setVisible();

Are there exceptions thrown? If so please post the entire stack trace...for instance, calling

frame[1].setVisible(true);

in one of the initialization loops should result in a NullPointerException

I noticed that, and it was fixed. oddly it didn't throw a nullpointer exception.

And I'll try that e.getActionCommand()

Alright I got it displaying, now I'm getting a NullPointException at

 scores = sg.getTestGrades();

Any help at all?

Initialize sp.

You must never have initialized it.

Simple. A NullPointerException indicates that you are attempting to dereference a variable that hasn't been initialized, or has had its value set to null. If the line you posted is giving rise to the exception, sg is null.

Trace the code execution and find out why a value hasn't been assigned to sg.

db

edit :humph: No response for nearly 2 hours and the penguin gets in a minute before me

I know I initialized sg. I always hit the construct button before I hit any of the action buttons.

When I hit my Action 1 button, it gives me a NPE for scores.
I know scores is set to null, but why won't it take the returned array?

I've gotten the JFrames fixed. I entirely eliminated the use of the JFrame array.