Thread: Help in Java

hello everyone : I dont understand why we need to first declare the boolean as false :boolean clickControl = false;
and then true and then true again please help .... here is the code:

import java.awt.*;
import java.awt.geom.*;
import javax.swing.*;
import java.awt.event.MouseListener;
import java.awt.event.MouseEvent;
 
 
public class Week1MouseEventsQ6 extends JFrame
{
	DrawPanel canvas;
 
	public static void main(String[] args)
	{
		Week1MouseEventsQ6 w = new Week1MouseEventsQ6();
		w.setVisible(true);
	}
 
	public Week1MouseEventsQ6()
	{
		setTitle("Week2MouseEvents: starting code");
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setSize(500,220);
		setLocation(300,300);
		canvas = new DrawPanel(7, 5);
		add(canvas);
 	}
 
	class DrawPanel extends JPanel implements MouseListener
	{
		int numCols;
		int numRows;
 
		int clickColumnIndex = -1;
		int clickRowIndex = -1;
 
		int buttonNumber = 0;
 
		boolean clickControl = false;
 
		public void mouseReleased(MouseEvent event)
		{
			System.out.println("Mouse Released");
			System.out.println("X: " + event.getX() + "Y: " + event.getY());
		}
		public void mousePressed(MouseEvent event)
		{
			System.out.println("Mouse Pressed");
			System.out.println("X: " + event.getX() + "Y: " + event.getY());
		}
		public void mouseClicked(MouseEvent event)
		{
			buttonNumber = event.getButton();
 
			clickColumnIndex = (numCols) * (event.getX()) / (getWidth());
			clickRowIndex = (numRows) * (event.getY()) / (getHeight());
 
			clickControl = true;
 
			System.out.println("Mouse Clicked");
			System.out.println("X: " + event.getX() + "Y: " + event.getY());
			System.out.println("Row " + clickRowIndex + "Column " + clickColumnIndex);
 
			repaint();
 
		}
		public void mouseEntered(MouseEvent event)
		{
			System.out.println("Mouse Entered");
			System.out.println("X: " + event.getX() + "Y: " + event.getY());
		}
		public void mouseExited(MouseEvent event)
		{
			System.out.println("Mouse Exited");
			System.out.println("X: " + event.getX() + "Y: " + event.getY());
		}
 
 
		public DrawPanel(int nc, int nr)
		{
			numCols = nc;
			numRows = nr;
 
			addMouseListener(this);
		}
 
		Rectangle getRect(int thisCol, int thisRow)
		{
			// if input is out of range, return "null"
			if(thisCol <0 || thisRow < 0)
				return null;
			if(thisCol>=numCols || thisRow>=numRows)
				return null;
 
			// otherwise, make and return the Rectangle
			int w = getWidth()/numCols;
			int h = getHeight()/numRows;
 
			int x = thisCol*w;
			int y = thisRow*h;
 
			Rectangle myRect = new Rectangle(x,y,w,h);
			return myRect;
		}
 
		public void paint(Graphics g)
		{
			g.setColor(Color.gray);
			g.fillRect(0,0,getWidth(), getHeight());
			g.setColor(Color.black);
 
 
			Graphics2D g2 = (Graphics2D)g;
			// we'll use Graphics2D for it's "draw" method -
			// neater than the Graphics "drawRect" suppled
			// (which you could also use)
 
			for (int i = 0;i<numCols;i++)
				for(int j = 0;j<numRows;j++)
					g2.draw(getRect(i,j));
 
			if (clickControl == true)
			{
			Rectangle r2 = getRect(clickColumnIndex,clickRowIndex);
			g.setColor(Color.red);
			g.fillOval(r2.x,r2.y,r2.width, r2.height);
			}
 
			if (buttonNumber == 3)
			{
			Rectangle r3 = getRect(clickColumnIndex,clickRowIndex);
			g.setColor(Color.yellow);
			g.fillOval(r3.x,r3.y,r3.width, r3.height);
			}
 
		}
 
	}
 
 }