Random Shape Generator

**sjdganc** · August 31st, 2014, 11:27 AM

I am trying to get random shapes to generate automatically. I was able to get just three shapes to generate but nothing random. When I added the random code now only the frame shows up and no shapes. I also keep getting an error with frame.setVisible(true). It says identifier expected. Thanks for the help. Here is what I have so far:
Main program
//Fundamentals of Java, Lab 4, Part 2

import javax.swing.*;
import java.awt.*;
import java.util.Random;

public class ShapeGen {

public static void main(String [] args) {

//Create window and set title
draw panel = new Draw();
JFrame frame = new JFrame();
frame.setTitle("Random Shape Generator");

//Close the window, add to panel, set size and visibility
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOS E);
frame.add( panel );
frame.setSize( 600, 300);
frame.setVisible( true );

}

}

This is the draw program to generate random shapes:
import javax.swing.*;
import java.awt.*;
import java.util.Random;

public class draw extends JPanel {

public draw(Color backColor) {
setBackground(backColor);
}

//variable to hold the shape
int shape;

private static final Random gen = new Random();

public void paintComponent(Graphics g) {

super.paintComponent(g);
//g.setColor(Color.BLACK);
//g.fillOval(20, 50, 100, 50);
//g.setColor(Color.BLUE);
//g.fillOval(150, 25, 100, 100);
//g.setColor(Color.RED);
//g.fillRect(275, 25, 100, 100);

for(int i = 0; i < 4; i++) {

switch (shape) {

case '1':
g.setColor(Color.BLACK);
g.fillOval(20, 50, 100, 50);
break;
case '2':
g.setColor(Color.BLUE);
g.fillOval(150, 25, 100, 100);
break;
case '3':
g.setColor(Color.RED);
g.fillRect(275, 25, 100, 100);
break;
}

}
}
public static int chooseShape() {
int theShape = 1 + gen.nextInt(3);
return theShape;

}

}

**Norm** · August 31st, 2014, 11:30 AM

I also keep getting an error

Please copy the full text of the error message and paste it here.

Please edit your post and wrap your code with code tags:
[code=java]
YOUR CODE GOES HERE
[/code]
to get highlighting and preserve formatting.

**sjdganc** · August 31st, 2014, 11:50 AM

Ok, thank you. I have some code commented out in the main program so that I did not lose what I had working at one point.

import javax.swing.*;
import java.awt.*;
import java.util.Random;
 
 
public class ShapeGen {
 
	public static void main(String [] args) {
 
		//Create window and set title
		draw panel = new Draw();
		JFrame frame = new JFrame();
		frame.setTitle("Random Shape Generator");
 
		//Close the window, add to panel, set size and visibility
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.add( panel );
		frame.setSize( 600, 300);
		frame.setVisible( true );
 
		//Container pane = frame.getContentPane();
		//pane.setLayout(new GridLayout(5, 5));
 
 
	}
 
 
	//Color backColor = new Color(red, green, blue);
	//Panel panel = new Panel();
	//panel.setBackground(backColor);
	//pane.add(panel);		
 
 
	//set window to visible
	frame.setVisible( true );
 
	//draw object = new draw();
	//frame.add(object);
 
	//object.drawing();	
	}
 
}

import javax.swing.*;
import java.awt.*;
import java.util.Random;
 
 
public class draw extends JPanel {
 
 
	public draw(Color backColor) {
		setBackground(backColor);
	}
 
	//variable to hold the shape
	int shape;
 
	private static final Random gen = new Random();
 
 
	public void paintComponent(Graphics g) {				
 
		super.paintComponent(g);
		//g.setColor(Color.BLACK);
		//g.fillOval(20, 50, 100, 50);
		//g.setColor(Color.BLUE);
		//g.fillOval(150, 25, 100, 100);
		//g.setColor(Color.RED);
		//g.fillRect(275, 25, 100, 100);
 
 
		for(int i = 0; i < 4; i++) {
 
			switch (shape) {
 
				case '1':
					g.setColor(Color.BLACK);
					g.fillOval(20, 50, 100, 50);
					break;
				case '2':
					g.setColor(Color.BLUE);
					g.fillOval(150, 25, 100, 100);
					break;
				case '3':
					g.setColor(Color.RED);
					g.fillRect(275, 25, 100, 100);
					break;
			}			
 
		}
	}
	public static int chooseShape() {
		int theShape = 1 + gen.nextInt(3);
		return theShape;	
 
	}
}

Here are there errors:
ShapeGen.java:37: error: <identifier> expected
frame.setVisible( true );
ShapeGen.java:37: errorL illegal start of type
frame.setVisible( true );
ShapeGen.java:45: error: class, interface, or enum expected }

**Norm** · August 31st, 2014, 11:56 AM

ShapeGen.java:37: error: <identifier> expected

Is the code on line 37 inside of a method?

**sjdganc** · August 31st, 2014, 12:47 PM

No, I had it outside of the brackets. Thank you for pointing that out. When I fixed that I realized the third error expecting the } so I fixed that. Now I am getting this error:
ShapeGen.java:13: error: cannot find symbol
draw panel = new Draw();
symbol: class Draw
location: class ShapeGen

--- Update ---

I've played with this code some more and I don't get any errors but I only get a yellow window. No shapes.

import javax.swing.*;
import java.awt.*;
import java.util.Random;
 
 
public class ShapeGen {
 
	public static void main(String [] args) {
 
		//Create window and set title
		JFrame frame = new JFrame();
		frame.setTitle("Random Shape Generator");
		frame.setSize(600, 300);
 
		//Close the window 
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
		//Create panel and add to window pane
		JPanel panel = new JPanel();
		panel.setBackground(Color.orange);
		Container pane = frame.getContentPane();
		pane.add(panel);
 
		//make window visible
		frame.setVisible(true);
 
	}
 
}

import javax.swing.*;
import java.awt.*;
import java.util.Random;
 
 
public class draw extends JPanel {
 
 
	public draw(Color backColor) {
		setBackground(backColor);
	}
 
	//variable to hold the shape
	int shape;
 
	private static final Random gen = new Random();
 
 
	public void paintComponent(Graphics g) {				
 
		super.paintComponent(g);
		//g.setColor(Color.BLACK);
		//g.fillOval(20, 50, 100, 50);
		//g.setColor(Color.BLUE);
		//g.fillOval(150, 25, 100, 100);
		//g.setColor(Color.RED);
		//g.fillRect(275, 25, 100, 100);
 
 
		for(int i = 0; i < 4; i++) {
 
			switch (shape) {
 
				case '1':
					g.setColor(Color.BLACK);
					g.fillOval(20, 50, 100, 50);
					break;
				case '2':
					g.setColor(Color.BLUE);
					g.fillOval(150, 25, 100, 100);
					break;
				case '3':
					g.setColor(Color.RED);
					g.fillRect(275, 25, 100, 100);
					break;
			}			
 
		}
	}
	public static int chooseShape() {
		int theShape = 1 + gen.nextInt(3);
		return theShape;	
 
	}
}

**Norm** · August 31st, 2014, 12:51 PM

ShapeGen.java:13: error: cannot find symbol
draw panel = new Draw();
symbol: class Draw

The compiler can not find a class named: Draw. Java is case-sensitive so draw is not the same as Draw

**sjdganc** · August 31st, 2014, 01:38 PM

Do I need that in the draw program? I changed it to the below code. I get just a yellow window to display, but no shapes.

import javax.swing.*;
import java.awt.*;
import java.util.Random;
 
 
public class ShapeGen {
 
	public static void main(String [] args) {
 
		//Create window and set title
		JFrame frame = new JFrame();
		frame.setTitle("Random Shape Generator");
		frame.setSize(600, 300);
 
		//Close the window 
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
		//Create panel and add to window pane
		JPanel panel = new JPanel();
		panel.setBackground(Color.orange);
		Container pane = frame.getContentPane();
		pane.add(panel);
 
		//make window visible
		frame.setVisible(true);
 
	}
 
}

**Norm** · August 31st, 2014, 01:43 PM

the below code. I get just a yellow window to display, but no shapes.

Where does that code create any shapes?
If the shapes are drawn in another class, that other class needs to be included.

**sjdganc** · August 31st, 2014, 01:53 PM

This code is supposed to run the shapes in the draw program. I added a draw object to the ShapeGen code but get the below errors:
ShapeGen.java:29: error: constructor draw in class draw cannot be applied to given types:
draw object = new draw();
required: Color
found: no arguments
reason: actual and formal argument lists differ in length

ShapeGen.java:31: error: cannot find symbol
object.draw();
symbol: method draw()
location: variable object of type draw

import javax.swing.*;
import java.awt.*;
import java.util.Random;
 
 
public class ShapeGen {
 
	public static void main(String [] args) {
 
		//Create window and set title
		JFrame frame = new JFrame();
		frame.setTitle("Random Shape Generator");
		frame.setSize(600, 300);
 
		//Close the window 
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
		//Create panel and add to window pane
		JPanel panel = new JPanel();
		panel.setBackground(Color.orange);
		Container pane = frame.getContentPane();
		pane.add(panel);
 
		//make window visible
		frame.setVisible(true);
 
		draw object = new draw();
		frame.add(object);
		object.draw();		
 
	}
 
 
}

import javax.swing.*;
import java.awt.*;
import java.util.Random;
 
 
public class draw extends JPanel {
 
 
	public draw(Color backColor) {
		setBackground(backColor);
	}
 
	//variable to hold the shape
	int shape;
 
	private static final Random gen = new Random();
 
 
	public void paintComponent(Graphics g) {				
 
		super.paintComponent(g);
		//g.setColor(Color.BLACK);
		//g.fillOval(20, 50, 100, 50);
		//g.setColor(Color.BLUE);
		//g.fillOval(150, 25, 100, 100);
		//g.setColor(Color.RED);
		//g.fillRect(275, 25, 100, 100);
 
 
		for(int i = 0; i < 4; i++) {
 
			switch (shape) {
 
				case '1':
					g.setColor(Color.BLACK);
					g.fillOval(20, 50, 100, 50);
					break;
				case '2':
					g.setColor(Color.BLUE);
					g.fillOval(150, 25, 100, 100);
					break;
				case '3':
					g.setColor(Color.RED);
					g.fillRect(275, 25, 100, 100);
					break;
			}			
 
		}
	}
	public static int chooseShape() {
		int theShape = 1 + gen.nextInt(3);
		return theShape;	
 
	}
}

**Norm** · August 31st, 2014, 02:04 PM

draw object = new draw();
required: Color
found: no arguments
reason: actual and formal argument lists differ in length

The compiler could not find a no-arg constructor in the Draw class.
It did find a constructor that takes a Color object.

To make the compiler happy:
either add a constructor to Draw that has no arguments
or change the new statement that calls the Draw's constructor to pass it a Color

BTW Java coding conventions want class names to start with uppercase letters: Draw vs draw

**sjdganc** · August 31st, 2014, 02:30 PM

I'm not sure what you mean by constructor. In the draw program do I change it to this

public draw() {
}

**Norm** · August 31st, 2014, 02:35 PM

That code looks like a no-arg constructor. Did you try it? What happened?

Take a look at the tutorial: http://docs.oracle.com/javase/tutori...structors.html

**sjdganc** · August 31st, 2014, 02:47 PM

I tried it and see from the tutorial you provided that it is a no-arg constructor, so I'm not telling it what I want to do, right? But in the ShapeGen program I get this error:
ShapeGen.java:32: error: cannot find symbol
object.draw();

symbol: method draw()
location: variable object of type draw

import javax.swing.*;
import java.awt.*;
import java.util.Random;
 
 
public class ShapeGen {
 
	public static void main(String [] args) {
 
 
		//Create window and set title
		JFrame frame = new JFrame();
		frame.setTitle("Random Shape Generator");
		frame.setSize(600, 300);
 
		//Close the window 
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
		//Create panel and add to window pane
		JPanel panel = new JPanel();
		panel.setBackground(Color.orange);
		Container pane = frame.getContentPane();
		pane.add(panel);
 
		//make window visible
		frame.setVisible(true);
 
		draw object = new draw();
		frame.add(object);
		object.draw();		
 
	}
 
 
}

**Norm** · August 31st, 2014, 02:53 PM

ShapeGen.java:32: error: cannot find symbol
object.draw();

symbol: method draw()
location: variable object of type draw

Where is the draw() method defined in the draw class? The compiler can not find it.

That is an example of why the naming conventions are helpful.
There is draw a class and draw a method.
It should be Draw the class and draw the method

**sjdganc** · August 31st, 2014, 03:04 PM

I'm trying to get this but I'm not quite understanding. So I changed the name of the draw program to Draw and left the constructor as public draw. I get this error on the Draw program

import javax.swing.*;
import java.awt.*;
import java.util.Random;
 
 
public class Draw extends JPanel {
 
 
	public draw() {
 
	}
 
	//variable to hold the shape
	int shape;
 
	private static final Random gen = new Random();
 
 
	public void paintComponent(Graphics g) {				
 
		super.paintComponent(g);
		//g.setColor(Color.BLACK);
		//g.fillOval(20, 50, 100, 50);
		//g.setColor(Color.BLUE);
		//g.fillOval(150, 25, 100, 100);
		//g.setColor(Color.RED);
		//g.fillRect(275, 25, 100, 100);
 
 
		for(int i = 0; i < 4; i++) {
 
			switch (shape) {
 
				case '1':
					g.setColor(Color.BLACK);
					g.fillOval(20, 50, 100, 50);
					break;
				case '2':
					g.setColor(Color.BLUE);
					g.fillOval(150, 25, 100, 100);
					break;
				case '3':
					g.setColor(Color.RED);
					g.fillRect(275, 25, 100, 100);
					break;
			}			
 
		}
	}
	public static int chooseShape() {
		int theShape = 1 + gen.nextInt(3);
		return theShape;	
 
	}
}

The error is:
Draw.java:9: error: invalid method declaration; return type required
public draw() {

**Norm** · August 31st, 2014, 03:12 PM

public draw() {

The spelling of the constructor's name must match the class's name.

What happened to the constructor that takes a color? A class can have many different constructors.

**sjdganc** · August 31st, 2014, 03:47 PM

Ok, I see that. Thank you. So the Draw program new code compiles without error but I get a new error in the ShapeGen program.

import javax.swing.*;
import java.awt.*;
import java.util.Random;
 
 
public class Draw extends JPanel {
 
 
	public Draw(Color backColor) {
		setBackground(backColor);
	}
 
 
 
	//variable to hold the shape
	int shape;
 
	private static final Random gen = new Random();
 
 
	public void paintComponent(Graphics g) {				
 
		super.paintComponent(g);
		//g.setColor(Color.BLACK);
		//g.fillOval(20, 50, 100, 50);
		//g.setColor(Color.BLUE);
		//g.fillOval(150, 25, 100, 100);
		//g.setColor(Color.RED);
		//g.fillRect(275, 25, 100, 100);
 
 
		for(int i = 0; i < 4; i++) {
 
			switch (shape) {
 
				case '1':
					g.setColor(Color.BLACK);
					g.fillOval(20, 50, 100, 50);
					break;
				case '2':
					g.setColor(Color.BLUE);
					g.fillOval(150, 25, 100, 100);
					break;
				case '3':
					g.setColor(Color.RED);
					g.fillRect(275, 25, 100, 100);
					break;
			}			
 
		}
	}
	public static int chooseShape() {
		int theShape = 1 + gen.nextInt(3);
		return theShape;	
 
	}
}

import javax.swing.*;
import java.awt.*;
import java.util.Random;
 
 
public class ShapeGen {
 
	public static void main(String [] args) {
 
 
		//Create window and set title
		JFrame frame = new JFrame();
		frame.setTitle("Random Shape Generator");
		frame.setSize(600, 300);
 
		//Close the window 
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
		//Create panel and add to window pane
		JPanel panel = new JPanel();
		panel.setBackground(Color.orange);
		Container pane = frame.getContentPane();
		pane.add(panel);
 
		//make window visible
		frame.setVisible(true);
 
		Draw object = new Draw();
		frame.add(object);
		object.Draw();		
 
	}
 
 
}

I thought what I have at the end is drawing the object but these are the errors:
ShapeGen.java:30: error: cannot find symbol
Draw object = new Draw();
symbol: class Draw
location: class ShapeGen
ShapeGen.java:30: error: cannot find symbol
Draw object = new Draw();
symbol: class Draw
location: class ShapeGen

Do I have the last 3 lines of code in the ShapeGen in the wrong program?

**Norm** · August 31st, 2014, 04:04 PM

ShapeGen.java:30: error: cannot find symbol
Draw object = new Draw();
symbol: class Draw

Where is the no-arg constructor for the Draw class?

**sjdganc** · August 31st, 2014, 04:11 PM

I put that back in in the Draw class and it compiles with no errors. But still get the same above errors:

import javax.swing.*;
import java.awt.*;
import java.util.Random;
 
 
public class Draw extends JPanel {
 
 
	public Draw() {
	}
 
 
	public Draw(Color backColor) {
		setBackground(backColor);
	}
 
 
	//variable to hold the shape
	int shape;
 
	private static final Random gen = new Random();
 
 
	public void paintComponent(Graphics g) {				
 
		super.paintComponent(g);
		//g.setColor(Color.BLACK);
		//g.fillOval(20, 50, 100, 50);
		//g.setColor(Color.BLUE);
		//g.fillOval(150, 25, 100, 100);
		//g.setColor(Color.RED);
		//g.fillRect(275, 25, 100, 100);
 
 
		for(int i = 0; i < 4; i++) {
 
			switch (shape) {
 
				case '1':
					g.setColor(Color.BLACK);
					g.fillOval(20, 50, 100, 50);
					break;
				case '2':
					g.setColor(Color.BLUE);
					g.fillOval(150, 25, 100, 100);
					break;
				case '3':
					g.setColor(Color.RED);
					g.fillRect(275, 25, 100, 100);
					break;
			}			
 
		}
	}
	public static int chooseShape() {
		int theShape = 1 + gen.nextInt(3);
		return theShape;	
 
	}
}

**Norm** · August 31st, 2014, 04:13 PM

Please copy and paste the current errors. There have been lots of them posted and I'm not sure which youy are talking about.

ALSO: There should be a default: case in the switch statement that prints a message if none of the other case statements were true.

**sjdganc** · August 31st, 2014, 04:21 PM

When I comment these three lines out I get the orange box but still no shapes. In other examples I have seen where the for loop should be in the main method. Is this part of my problem or am I jumping ahead?

//Draw object = new Draw();
//frame.add(object);
//object.Draw();

--- Update ---

Here are the current errors:
ShapeGen.java:30: error: cannot find symbol
Draw object = new Draw();
symbol: class Draw
location: class ShapeGen

ShapeGen.java:30: error: cannot find symbol
Draw object = new Draw();
symbol: class Draw
location: class ShapeGen

I am not that familiar with switch...case. If I can do it in a for loop instead can you suggest how?

**Norm** · August 31st, 2014, 04:25 PM

ShapeGen.java:30: error: cannot find symbol
Draw object = new Draw();
symbol: class Draw

Does the Draw class have a no-arg constructor?

I am not that familiar with switch...case.

See the tutorial: http://docs.oracle.com/javase/tutori...ts/switch.html

can do it

Please describe what "it" is supposed to mean.

**sjdganc** · August 31st, 2014, 04:38 PM

I thought

public Draw() {
}

is the no-arg constructor. But I see I don't have it doing anything, so I added:

public Draw() {
    shape = 4;
}

hoping this would create 4 shapes. I declared the variable int shape; above the constructor.

By "it" I was referring to create the shapes by using a for loop in the main program instead of in the draw program.

**Norm** · August 31st, 2014, 04:54 PM

Yes, that looks like a no-arg constructor.

create the shapes by using a for loop in the main program instead of in the draw program.

The drawing of the shapes is done in the paintComponent() method. I'm not sure what you mean by "create" the shapes. The switch statement in the paintComponent() method will draw one of 4 shapes depending on the switch value.
I don't know what the for loop is for. I don't see what is being changed inside the loop as the loop goes around. Why have a loop if nothing changes inside of the loop?

One problem I just saw is the adding of the Draw object AFTER the frame is setVisible. The new addition won't be shown until something makes the frame be drawn again. Move setVisible() call to AFTER everything to be show has been added to the frame.

**sjdganc** · August 31st, 2014, 05:09 PM

I moved setVisible() to after everything as you suggested but still get the same errors as most recently stated above. I also see your points about the for loop so I commented those out for now and made some changes to the Draw program:

import javax.swing.*;
import java.awt.*;
import java.util.Random;
 
 
public class Draw extends JPanel {
 
	int shape;
 
	public Draw() {
 
		shape = 4;
 
	}
 
 
	public Draw(Color backColor) {
		setBackground(backColor);
	}
 
 
	//variable to hold the shape
	//int shape;
 
	private static final Random gen = new Random();
 
 
	public void paintComponent(Graphics g) {				
 
		super.paintComponent(g);
		//g.setColor(Color.BLACK);
		//g.fillOval(20, 50, 100, 50);
		//g.setColor(Color.BLUE);
		//g.fillOval(150, 25, 100, 100);
		//g.setColor(Color.RED);
		//g.fillRect(275, 25, 100, 100);
 
 
		//for(int i = 0; i < 4; i++) {
 
		shape = chooseShape();   //added this
		switch (shape) {
 
			case '1':
				g.setColor(Color.BLACK);
				g.fillOval(20, 50, 100, 50);
				break;
			case '2':
				g.setColor(Color.BLUE);
				g.fillOval(150, 25, 100, 100);
				break;
			case '3':
				g.setColor(Color.RED);
				g.fillRect(275, 25, 100, 100);
				break;
			}			
 
		//}
	}
	public static int chooseShape() {
		int theShape = 1 + gen.nextInt(3);
		return theShape;	
 
	}
}

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