Help Centos 7 server

VDSystemManager: ----------------------- VDS Manager ----------------------- Configurations: loaded. Exception in thread "main" java.lang.ExceptionInInitializerError at itopz.com.gui.Gui.getInstance(Gui.java:243) at itopz.com.VDSystemManager.<init>(VDSystemManager.java:55) at itopz.com.VDSystemManager$SingletonHolder.<clinit>(VDSystemManager.java:79) at itopz.com.VDSystemManager.getInstance(VDSystemManager.java:74) at net.sf.l2j.gameserver.GameServer.<init>(GameServer.java:417) at net.sf.l2j.gameserver.GameServer.main(GameServer.java:502) Caused by: java.awt.HeadlessException: No X11 DISPLAY variable was set, but this program performed an operation which requires it. at java.desktop/java.awt.GraphicsEnvironment.checkHeadless(GraphicsEnvironment.java:208) at java.desktop/java.awt.Window.<init>(Window.java:548) at java.desktop/java.awt.Frame.<init>(Frame.java:423) at java.desktop/java.awt.Frame.<init>(Frame.java:388) at java.desktop/javax.swing.JFrame.<init>(JFrame.java:180) at itopz.com.gui.Gui.<init>(Gui.java:61) at itopz.com.gui.Gui$SingletonHolder.<clinit>(Gui.java:248) ... 6 more wrote: