can't Edit and create new transformation in pentaho data integration

Question

I am new to Pentaho and facing an issue when editing or creating new transformation in spoon. Below are the details of problem.

java.lang.NullPointerException
    at org.pentaho.di.ui.core.database.dialog.XulDatabaseDialog.open(XulDatabaseDialog.java:111)
    at org.pentaho.di.ui.core.database.dialog.DatabaseDialog.open(DatabaseDialog.java:59)
    at org.pentaho.di.ui.trans.step.BaseStepDialog$5.widgetSelected(BaseStepDialog.java:770)
    at org.eclipse.swt.widgets.TypedListener.handleEvent(Unknown Source)
    at org.eclipse.swt.widgets.EventTable.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Unknown Source)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Unknown Source)
    at org.pentaho.di.ui.trans.steps.databasejoin.DatabaseJoinDialog.open(DatabaseJoinDialog.java:415)
    at org.pentaho.di.ui.spoon.delegates.SpoonStepsDelegate.editStep(SpoonStepsDelegate.java:124)
    at org.pentaho.di.ui.spoon.Spoon.editStep(Spoon.java:8720)
    at org.pentaho.di.ui.spoon.trans.TransGraph.editStep(TransGraph.java:3027)
    at org.pentaho.di.ui.spoon.trans.TransGraph.mouseDoubleClick(TransGraph.java:744)
    at org.eclipse.swt.widgets.TypedListener.handleEvent(Unknown Source)
    at org.eclipse.swt.widgets.EventTable.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Unknown Source)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Unknown Source)
    at org.pentaho.di.ui.spoon.Spoon.readAndDispatch(Spoon.java:1310)
    at org.pentaho.di.ui.spoon.Spoon.waitForDispose(Spoon.java:7931)
    at org.pentaho.di.ui.spoon.Spoon.start(Spoon.java:9202)
    at org.pentaho.di.ui.spoon.Spoon.main(Spoon.java:648)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:564)
    at org.pentaho.commons.launcher.Launcher.main(Launcher.java:92)

Answer 1

As you have known by now, the null pointer exception is due to the reason it cannot locate the relevant java libraries. So you must have the paths defined for Java and kettle.