added new filter method

Issue #238

open-bpmn.metamodel/src/main/java/org/openbpmn/bpmn/elements/BPMNProcess.java

@@ -3,6 +3,7 @@
 import java.util.Iterator;
 import java.util.LinkedHashSet;
 import java.util.Set;
+import java.util.function.Predicate;
 import java.util.logging.Logger;
 
 import org.openbpmn.bpmn.BPMNModel;
@@ -1057,6 +1058,26 @@ public BPMNElementNode findElementNodeById(String id) {
         return null;
     }
 
+    /**
+     * Returns a filtered list of elements
+     * 
+     * @param <T>
+     * 
+     * @param <T>
+     * @param id
+     * @return
+     */
+    public <T> Set<? extends BPMNElementNode> findElementNodes(Predicate<BPMNElementNode> filter) {
+        Set<BPMNElementNode> result = new LinkedHashSet<BPMNElementNode>();
+        Set<BPMNElementNode> allElements = this.getAllElementNodes();
+        for (BPMNElementNode _node : allElements) {
+            if (filter.test(_node)) {
+                result.add(_node);
+            }
+        }
+        return result;
+
+    }
     /**
      * Returns all BPMNFlowElements contained in this process
      * 

open-bpmn.metamodel/src/test/java/org/openbpmn/metamodel/navigation/TestFilter.java

@@ -0,0 +1,52 @@
+package org.openbpmn.metamodel.navigation;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+import java.util.Set;
+import java.util.logging.Logger;
+
+import org.junit.jupiter.api.Test;
+import org.openbpmn.bpmn.BPMNModel;
+import org.openbpmn.bpmn.BPMNTypes;
+import org.openbpmn.bpmn.elements.BPMNProcess;
+import org.openbpmn.bpmn.elements.core.BPMNElementNode;
+import org.openbpmn.bpmn.exceptions.BPMNModelException;
+import org.openbpmn.bpmn.util.BPMNModelFactory;
+import org.openbpmn.metamodel.examples.TestCreateEdges;
+
+/**
+ * This JUnit test verifies the filter methods
+ * 
+ */
+public class TestFilter {
+    private static Logger logger = Logger.getLogger(TestCreateEdges.class.getName());
+
+    /**
+     * Loads a model and test the filter method.
+     * 
+     * The method applies a filter to match ThrowEvents only within a process.
+     * 
+     * @throws BPMNModelException
+     * 
+     */
+    @Test
+    public void testFilterMethod() throws BPMNModelException {
+
+        logger.info("...read model");
+        BPMNModel model = BPMNModelFactory.read("/refmodel-15.bpmn");
+
+        assertEquals(1, model.getProcesses().size());
+        BPMNProcess process = model.openDefaultProces();
+
+        Set<? extends BPMNElementNode> throwEvents = process
+                .findElementNodes(n -> BPMNTypes.THROW_EVENT.equals(n.getType()));
+
+        assertNotNull(throwEvents);
+        // We expect exactly one result.
+
+        assertEquals(1, throwEvents.size());
+
+    }
+
+}