Java in Linux - different look and feel classes for root and non-root

Question

I noticed that Java proposes different look and feel classes for root and non-root users. I am trying to understand how to make LAF consistent. Moreover, it's inconsistent even within a user/root: depends on how user/root logged in:

Sample code (compiled and packaged in laf.jar):

import javax.swing.UIManager;

public class laf {
    public static void main(java.lang.String[] args) {
        try {
            System.out.print(UIManager.getSystemLookAndFeelClassName());
        } catch (Exception e) {
        }
    }
}

Scenario 1 Logs in to machine (in GUI mode) as a regular user

Sample output (as user)

[xxx@yyy Downloads]$ java -classpath laf.jar laf
com.sun.java.swing.plaf.gtk.GTKLookAndFeel

Sample output (switch to root via su)

[root@yyy Downloads]# java -classpath ./laf.jar laf
javax.swing.plaf.metal.MetalLookAndFeel

Scenario 2 Logs in to machine (in GUI mode) as root

Sample output (as root)

[root@yyy Downloads]# java -classpath ./laf.jar laf
com.sun.java.swing.plaf.gtk.GTKLookAndFeel

Scenario 3 Logs in to machine via SSH as a regular user (similar as scenario #1 above, but in this case - same LAF)

Sample output (as user)

[xxx@yyy Downloads]$ java -classpath laf.jar laf
javax.swing.plaf.metal.MetalLookAndFeel

Sample output (switch to root)

[root@yyy Downloads]# java -classpath ./laf.jar laf
javax.swing.plaf.metal.MetalLookAndFeel

Software versions:

[root@yyy Downloads]# java -version
java version "1.7.0"
Java(TM) SE Runtime Environment (build pxa6470sr9fp10-20150708_01(SR9 FP10))
IBM J9 VM (build 2.6, JRE 1.7.0 Linux amd64-64 Compressed References     20150701_255667 (JIT enabled, AOT enabled)
J9VM - R26_Java726_SR9_20150701_0050_B255667
JIT  - tr.r11_20150626_95120.01
GC   - R26_Java726_SR9_20150701_0050_B255667_CMPRSS
J9CL - 20150701_255667)
JCL - 20150628_01 based on Oracle jdk7u85-b15

[root@yyy Downloads]# cat /etc/redhat-release 
Red Hat Enterprise Linux Workstation release 6.7 (Santiago)

Answer 1

The first line of getSystemLookAndFeelClassName is:

public static String getSystemLookAndFeelClassName() {
    String systemLAF = AccessController.doPrivileged(
                         new GetPropertyAction("swing.systemlaf"));

So you can use the JAVA_OPTS of the user to set

-Dswing.systemlaf=javax.swing.plaf.metal.MetalLookAndFeel

As default.

add this to the .rc-File of the user:

set JAVA_OPTS=-Dswing.systemlaf=javax.swing.plaf.metal.MetalLookAndFeel
export JAVA_OPTS

Regards