It is showing a very large popup error with this trimmed error: I have used Android Studio earlier and now unable to launch it due to reasons I am unaware of. The last time I used Android Studio, I had only updated it and didn't do much of any development or worked on any project. I launched my AS after about 2 weeks and this is what I see.
Internal error. Please report to https://code.google.com/p/android/issues
java.lang.NoClassDefFoundError: com/google/api/client/auth/oauth2/Credential
at com.google.gct.login.GoogleLogin.createGoogleLoginState(GoogleLogin.java:503)
at com.google.gct.login.GoogleLogin.access$800(GoogleLogin.java:58)
at com.google.gct.login.GoogleLogin$AndroidPreferencesOAuthDataStore.initializeUsers(GoogleLogin.java:708)
at com.google.gct.login.GoogleLogin.getInstance(GoogleLogin.java:84)
at com.google.gct.login.ui.GoogleLoginActionButton.<init>(GoogleLoginActionButton.java:40)
at com.google.gct.login.ui.GoogleLoginAction.createCustomComponent(GoogleLoginAction.java:42)
at com.intellij.openapi.actionSystem.impl.ActionToolbarImpl.getCustomComponent(ActionToolbarImpl.java:330)
at com.intellij.openapi.actionSystem.impl.ActionToolbarImpl.fillToolBar(ActionToolbarImpl.java:310)
at com.intellij.openapi.actionSystem.impl.ActionToolbarImpl.updateActionsImpl(ActionToolbarImpl.java:894)
at com.intellij.openapi.actionSystem.impl.ActionToolbarImpl.access$000(ActionToolbarImpl.java:61)
at com.intellij.openapi.actionSystem.impl.ActionToolbarImpl$1.updateActionsImpl(ActionToolbarImpl.java:168)
at com.intellij.openapi.actionSystem.impl.ToolbarUpdater$MyUpdateRunnable.run(ToolbarUpdater.java:191)
at com.intellij.openapi.wm.impl.FocusManagerImpl.flushRequest(FocusManagerImpl.java:675)
at com.intellij.openapi.wm.impl.FocusManagerImpl.flushNow(FocusManagerImpl.java:656)
at com.intellij.openapi.wm.impl.FocusManagerImpl.flushIdleRequests(FocusManagerImpl.java:626)
at com.intellij.openapi.wm.impl.FocusManagerImpl.access$200(FocusManagerImpl.java:60)
at com.intellij.openapi.wm.impl.FocusManagerImpl$11.run(FocusManagerImpl.java:522)
at com.intellij.util.ui.UIUtil.invokeLaterIfNeeded(UIUtil.java:2379)
at com.intellij.openapi.wm.impl.FocusManagerImpl.doWhenFocusSettlesDown(FocusManagerImpl.java:500)
at com.intellij.openapi.actionSystem.impl.ToolbarUpdater.updateActions(ToolbarUpdater.java:108)
at com.intellij.openapi.actionSystem.impl.ToolbarUpdater.updateActions(ToolbarUpdater.java:93)
at com.intellij.openapi.actionSystem.impl.ActionToolbarImpl.setMiniMode(ActionToolbarImpl.java:1268)
at com.intellij.openapi.actionSystem.impl.ActionToolbarImpl.<init>(ActionToolbarImpl.java:184)
at com.intellij.openapi.actionSystem.impl.ActionToolbarImpl.<init>(ActionToolbarImpl.java:147)
at com.intellij.openapi.actionSystem.impl.ActionManagerImpl.createActionToolbar(ActionManagerImpl.java:471)
at com.intellij.openapi.actionSystem.impl.ActionManagerImpl.createActionToolbar(ActionManagerImpl.java:466)
at com.intellij.openapi.wm.impl.IdeRootPane.createToolbar(IdeRootPane.java:213)
at com.intellij.openapi.wm.impl.IdeRootPane.updateToolbar(IdeRootPane.java:193)
at com.intellij.openapi.wm.impl.IdeRootPane.<init>(IdeRootPane.java:99)
at com.intellij.openapi.wm.impl.IdeFrameImpl.createRootPane(IdeFrameImpl.java:184)
at com.intellij.openapi.wm.impl.IdeFrameImpl.<init>(IdeFrameImpl.java:96)
at com.intellij.openapi.wm.impl.WindowManagerImpl.showFrame(WindowManagerImpl.java:514)
at com.intellij.idea.IdeaApplication$IdeStarter.main(IdeaApplication.java:306)
at com.intellij.idea.IdeaApplication.run(IdeaApplication.java:172)
at com.intellij.idea.MainImpl$1$1$1.run(MainImpl.java:52)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:744)
at java.awt.EventQueue.access$400(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:697)
at java.awt.EventQueue$3.run(EventQueue.java:691)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:714)
at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.java:362)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
Caused by: java.lang.ClassNotFoundException: com.google.api.client.auth.oauth2.Credential PluginClassLoader[com.google.gct.login, 1.0]
at com.intellij.ide.plugins.cl.PluginClassLoader.loadClass(PluginClassLoader.java:68)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
Just resolved this issue by running the installer file which helped me to uninstall Android Studio keeping all the essential library files as it is and re-installing it in new empty directory. Everything is working fine like before now.