java - Swing Unable to draw circle -

so program wrote supposed draw circle everytime click on panel. reason have semicircle in top right hand corner upon startup, , can't draw circle. can see what's wrong it? circle should 20 px in diameter, drawn clicked point @ center.

    import java.awt.*;  import java.awt.event.*;  import javax.swing.*;    public class quizactionsinitial extends jframe {      public jbutton redbutton = new jbutton("red");      public jbutton clearbutton = new jbutton("clear");      boolean isred = false;      int x1,y1;      boolean clear = false;      circlepanel mypanel;    public quizactionsinitial() {       mypanel = new circlepanel();       add(mypanel, borderlayout.south);      jpanel southpanel = new jpanel(new flowlayout());       clearbutton.addactionlistener(new actionlistener(){          public void actionperformed(actionevent e){              clear = true;             }         });       mypanel.addmouselistener(new circlelistener());       southpanel.add(redbutton);      southpanel.add(clearbutton);      add(southpanel, borderlayout.north);      pack();      setvisible(true);  } // end constructor  public class circlepanel extends jpanel {      public circlepanel() {          setpreferredsize(new dimension(400,300));          setborder(borderfactory.createlineborder(color.blue, 2));         }       public void paintcomponent(graphics gc){          super.paintcomponent(gc);          gc.filloval(x1-10,y1-10,20,20);      }         } // end class circlepanel  // end class circlepanel   public class circlelistener extends mouseadapter{      public void mouseclicked(mouseevent e){          if (clear = false){              x1 = e.getx();              y1 = e.gety();            }          repaint();          clear = false;         }     }   public static void main(string args[]) {      new quizactionsinitial();     } // end main } // end class quizactionsinitial 

int x1,y1; initialise values 0, draw initial circle @ -10x-10

trying using java.awt.point class instead, , when it's null, don't paint anything...

//int x1,y1; private point point;  //... public void paintcomponent(graphics gc){      super.paintcomponent(gc);      if (point != null) {          gc.filloval(point.x-10,point.y-10,20,20);      } } //... public void mouseclicked(mouseevent e){     if (!clear){         point = evt.getpoint();     }     clear = false;     repaint(); } 

oh, , if (clear = false){ assignment (making clear equal false, if statement fail)