Description:
Although there is a package dependency on jre8-openjdk, the pycharm command apparently just uses the default java, as set by "archlinux-java set", instead of the java from jre8-openjdk.

On my system, I have both java-10-jdk and java-8-openjdk/jre installed. With the former set as the default, pycharm uses the java from java-10-jdk, throws an exception and fails to startup. With the latter set as the default, pycharm starts properly.

Additional info:
* Packages installed: community/pycharm-community-edition 2018.2-1, extra/jre8-openjdk 8.u172-2, aur/jdk 10.0.2-1
* Error:
Java HotSpot(TM) 64-Bit Server VM warning: Option UseConcMarkSweepGC was deprecated in version 9.0 and will likely be removed in a future release.
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.intellij.ide.ClassUtilCore to field sun.net.www.protocol.jar.JarFileFactory.fileCache
WARNING: Please consider reporting this to the maintainers of com.intellij.ide.ClassUtilCore
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

Start Failed: Internal error. Please report to http://jb.gg/ide/critical-startup-errors

java.lang.RuntimeException: com.intellij.ide.plugins.PluginManager$StartupAbortedException: Fatal error initializing 'com.intellij.ide.ui.LafManager'
at com.intellij.idea.IdeaApplication.run(IdeaApplication.java:213)
at com.intellij.idea.IdeaApplication.lambda$initApplication$0(IdeaApplication.java:72)
at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:313)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:770)
at java.desktop/java.awt.EventQueue.access$600(EventQueue.java:97)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:740)
at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.java:361)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
Caused by: com.intellij.ide.plugins.PluginManager$StartupAbortedException: Fatal error initializing 'com.intellij.ide.ui.LafManager'
at com.intellij.ide.plugins.PluginManager.handleComponentError(PluginManager.java:257)
at com.intellij.openapi.components.impl.PlatformComponentManagerImpl.handleInitComponentError(PlatformComponentManagerImpl.java:43)
at com.intellij.openapi.components.impl.ComponentManagerImpl$ComponentConfigComponentAdapter.getComponentInstance(ComponentManagerImpl.java:506)
at com.intellij.openapi.components.impl.ComponentManagerImpl.createComponents(ComponentManagerImpl.java:107)
at com.intellij.openapi.application.impl.ApplicationImpl.lambda$createComponents$9(ApplicationImpl.java:442)
at com.intellij.openapi.progress.impl.CoreProgressManager.lambda$runProcess$1(CoreProgressManager.java:157)
at com.intellij.openapi.progress.impl.CoreProgressManager.registerIndicatorAndRun(CoreProgressManager.java:580)
at com.intellij.openapi.progress.impl.CoreProgressManager.executeProcessUnderProgress(CoreProgressManager.java:525)
at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:85)
at com.intellij.openapi.progress.impl.CoreProgressManager.runProcess(CoreProgressManager.java:144)
at com.intellij.openapi.application.impl.ApplicationImpl.createComponents(ApplicationImpl.java:449)
at com.intellij.openapi.components.impl.ComponentManagerImpl.init(ComponentManagerImpl.java:91)
at com.intellij.openapi.application.impl.ApplicationImpl.load(ApplicationImpl.java:401)
at com.intellij.openapi.application.impl.ApplicationImpl.load(ApplicationImpl.java:387)
at com.intellij.idea.IdeaApplication.run(IdeaApplication.java:206)
... 16 more
Caused by: java.lang.NoClassDefFoundError: com/sun/java/swing/plaf/windows/WindowsLookAndFeel
at com.intellij.ide.ui.laf.IdeaLaf.initIdeaDefaults(IdeaLaf.java:81)
at com.intellij.ide.ui.laf.IdeaLaf.initComponentDefaults(IdeaLaf.java:28)
at java.desktop/javax.swing.plaf.basic.BasicLookAndFeel.getDefaults(BasicLookAndFeel.java:150)
at java.desktop/javax.swing.plaf.metal.MetalLookAndFeel.getDefaults(MetalLookAndFeel.java:1560)
at com.intellij.ide.ui.laf.darcula.DarculaLaf.getDefaults(DarculaLaf.java:95)
at java.desktop/javax.swing.UIManager.setLookAndFeel(UIManager.java:587)
at com.intellij.ide.ui.laf.LafManagerImpl.setCurrentLookAndFeel(LafManagerImpl.java:395)
at com.intellij.ide.ui.laf.LafManagerImpl.initComponent(LafManagerImpl.java:191)
at com.intellij.openapi.components.impl.ComponentManagerImpl$ComponentConfigComponentAdapter.getComponentInstance(ComponentManagerImpl.java:488)
... 28 more
Caused by: java.lang.ClassNotFoundException: com.sun.java.swing.plaf.windows.WindowsLookAndFeel
at com.intellij.util.lang.UrlClassLoader.findClass(UrlClassLoader.java:224)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:566)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:499)
... 37 more


Steps to reproduce:
1. Install above 3 packages.
2. archlinux-java set java-10-jdk
3. Start pycharm and witness the failure to start.