It's easier to copy and paste text from posted messages.
java.lang.IllegalArgumentException: adding a window to a container
at java.awt.Container.checkNotAWindow(Unknown Source)
at java.awt.Container.addImpl(Unknown Source)
at java.awt.Container.add(Unknown Source)
at javax.swing.JFrame.addImpl(Unknown Source)
at java.awt.Container.add(Unknown Source)
at gameWindow.Window.<init>(Window.java:18)
The code is trying to add an object that extends a window to a container at line 18 in the class Window.
The JVM does not allow that.
BTW Window is a Java class. Naming classes with the same name as java classes is confusing.