Ciao,
adesso ho forzato il valore a 0 con l'istruzione export come mi hai suggerito. Mi da però questo errore:
Codice PHP:
No protocol specified                                               
Exception in thread "main" java.lang.InternalError: Can't connect to X11 windowserver using ':0' as the value of the DISPLAY variable.
        at sun.awt.X11GraphicsEnvironment.initDisplay(Native Method)
        at sun.awt.X11GraphicsEnvironment.access$100(X11GraphicsEnvironment.java:62)
        at sun.awt.X11GraphicsEnvironment$1.run(X11GraphicsEnvironment.java:166)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.awt.X11GraphicsEnvironment.<clinit>(X11GraphicsEnvironment.java:142)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:186)
        at java.awt.GraphicsEnvironment.getLocalGraphicsEnvironment(GraphicsEnvironment.java:82)
        at sun.awt.X11.XToolkit.<clinit>(XToolkit.java:106)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:186)
        at java.awt.Toolkit$2.run(Toolkit.java:849)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.awt.Toolkit.getDefaultToolkit(Toolkit.java:841)
        at javax.swing.UIManager.getSystemLookAndFeelClassName(UIManager.java:600)
        at com.izforge.izpack.installer.GUIInstaller.loadLookAndFeel(GUIInstaller.java:264)
        at com.izforge.izpack.installer.GUIInstaller.<init>(GUIInstaller.java:100)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:532)
        at java.lang.Class.newInstance0(Class.java:372)
        at java.lang.Class.newInstance(Class.java:325)
        at com.izforge.izpack.installer.Installer.main(Installer.java:47)