请问这是什么原因？

亦风亦雨

Exception in thread "main" java.lang.InternalError: Can't connect to X11 window server using ':0.0' as the value of the DISPLAY variable.
        at sun.awt.X11GraphicsEnvironment.initDisplay(Native Method)
        at sun.awt.X11GraphicsEnvironment.access$000(X11GraphicsEnvironment.java:53)
        at sun.awt.X11GraphicsEnvironment$1.run(X11GraphicsEnvironment.java:142)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.awt.X11GraphicsEnvironment.<clinit>(X11GraphicsEnvironment.java:131)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:164)
        at java.awt.GraphicsEnvironment.getLocalGraphicsEnvironment(GraphicsEnvironment.java:68)
        at java.awt.Window.init(Window.java:270)

我的系统是Red Hat Enterprise Linux ES 3,开发环境是Eclipse 3.1,jdk1.5.0_04