Use Eclipse/Netbeans Java to run our program, but remember, title is called "Sourcejav", and following screenshot is showing this program running and output text. Please install the newest version of Java (Java 8 update 121), because the program only support for Java 8 update 121. Usage quote required (JPanel) is only support for Java 8 update 121, the Java 9 also support for code "JPanel a = new JPanel()" but Java 9 does not support for code "JPanel a = new JPanel("blah blah blah")". Actually, this code is not using in Java 9, so you do not install Java 9 in this reason, but also you can install Java 8 when you are using "JPanel a = new JPanel("blah blah blah")" on a line. Download Java 8 update 161 also you can do, but safely you just to run the Java support for the version Java 8 update 121 at the same time you do that.
Alternatively, Eclipse/Netbeans can run like "killall java" to stop your program and Eclipse/Netbea