JavaImports example: added check for possible Null-Pointer exception

If the example rule application fails to execute, then the graph may not
have any node. This case will now throw a corresponding Runtime
exception. This is relevant, e.g., if this example is used as a test
case for engine updates.

Change-Id: I849b01c2ec6c3eb96d6bb1e2f1502091a3a0f840
Signed-off-by: Frank HERMANN <frank.hermann-henshin@outlook.com>

1 files changed, 13 insertions, 1 deletions

diff --git a/plugins/org.eclipse.emf.henshin.examples/src/org/eclipse/emf/henshin/examples/javaimports/JavaImportsExample.java b/plugins/org.eclipse.emf.henshin.examples/src/org/eclipse/emf/henshin/examples/javaimports/JavaImportsExample.java
index 3d088049d..b916623e8 100644
--- a/plugins/org.eclipse.emf.henshin.examples/src/org/eclipse/emf/henshin/examples/javaimports/JavaImportsExample.java
+++ b/plugins/org.eclipse.emf.henshin.examples/src/org/eclipse/emf/henshin/examples/javaimports/JavaImportsExample.java
@@ -9,6 +9,8 @@
  */
 package org.eclipse.emf.henshin.examples.javaimports;
 
+import java.util.Iterator;
+
 import org.eclipse.emf.ecore.EObject;
 import org.eclipse.emf.henshin.interpreter.EGraph;
 import org.eclipse.emf.henshin.interpreter.Engine;
@@ -59,7 +61,17 @@ public class JavaImportsExample {
 		app.setParameterValue("x", value);
 		InterpreterUtil.executeOrDie(app);
 
-		EObject newObj = graph.iterator().next();
+		
+		
+		// retrieve the node that was created by the rule
+		Iterator<EObject> graphIt =graph.iterator(); 
+		EObject newObj = null;
+		if(graphIt.hasNext()) 
+			newObj = graphIt.next();
+		if(newObj==null) 
+			throw new RuntimeException("Unexpected result of rule application: no graph node was created (expected one node)");
+		
+		// retrieve the attribute value of the node and check the expected result
 		String newValue = (String) newObj.eGet(newObj.eClass().getEStructuralFeature("stringValue"));
 		if (!newValue.equals(value.toUpperCase())) {
 			throw new RuntimeException("Unexpected string value: \"" + newValue + "\" (expected \""