Exception in thread "main" java.lang.IllegalArgumentException: adding a window to a container --- What am I doing wrong? -

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• java.lang.illegalargumentexception: adding window container 2 answers

i have been having problem following:

package keyz;  import java.awt.color; import java.awt.graphics; import java.awt.event.keyevent; import java.awt.event.keylistener;  import javax.swing.jframe;  public class keypractise extends jframe{     public static int x;     public static int z;     public static float hue;      public static void main(string[] args) {         // todo auto-generated method stub         jframe window = new jframe("color square");         keypractise content = new keypractise((window.getwidth() / 2), window.getheight() / 2);         window.setcontentpane(content);         window.setsize(600,600);         window.setlocation(400,400);         window.setdefaultcloseoperation( jframe.exit_on_close );         window.setvisible(true);         content.requestfocusinwindow();         content.setbackground(color.white);     }      public keypractise (int xx, int zz){         xx = x;         zz = z;          listener listener = new listener();         addkeylistener(listener);      }      private class listener implements keylistener{          @override         public void keypressed(keyevent evt) {             // todo auto-generated method stub             int key = evt.getkeycode();              if (key == keyevent.vk_up){                 if ((hue + 0.00392) < 1.00000){                 hue += 0.00392;                 }                 if ((hue + 0.00392) >= 1.00000){                     hue -= hue;                 }                 repaint();             }           }//keypressed          @override         public void keyreleased(keyevent evt) {             // todo auto-generated method stub          }          @override         public void keytyped(keyevent evt) {             // todo auto-generated method stub          }          public void paintcomponent(graphics g) {              g.setcolor(color.gethsbcolor(hue, 1.0f, 1.0f));              g.fillrect(x, z, 50, 50);          }     } } 

i exception:

exception in thread "main" java.lang.illegalargumentexception: adding window container

i believe problem "adding window container." if so, other way can done avoid scenario?

also, told proper style add setbackground(color); method keypractise object constructor , add super.paintcomponent(g); paintcomponent() rather did. when error in eclipse:

the method paintcomponent(graphics) undefined type object

is bad use content.setbackground() in main subroutine?

thanks!

i have changed below line

public class keypractise extends jframe{ 

to

public class keypractise extends container{ 

and working now... please check