diff --git a/src/fdtmc/FDTMC.java b/src/fdtmc/FDTMC.java
index ef21282..78e9c2d 100644
--- a/src/fdtmc/FDTMC.java
+++ b/src/fdtmc/FDTMC.java
@@ -156,14 +156,20 @@ public Interface createInterface(String id, State initial, State success, State
 	                                           errorTransition);
 
 	    List<Interface> interfaceOccurrences = null;
-	    if (interfaces.containsKey(id)) {
+	    interfaceOccurrences = checkExistenceOfInterface(id);
+	    interfaceOccurrences.add(newInterface);
+	    return newInterface;
+	}
+
+	private List<Interface> checkExistenceOfInterface(String id) {
+		List<Interface> interfaceOccurrences;
+		if (interfaces.containsKey(id)) {
 	        interfaceOccurrences = interfaces.get(id);
 	    } else {
 	        interfaceOccurrences = new LinkedList<Interface>();
 	        interfaces.put(id, interfaceOccurrences);
 	    }
-	    interfaceOccurrences.add(newInterface);
-	    return newInterface;
+		return interfaceOccurrences;
 	}
 
 	public State getStateByLabel(String label) {
@@ -227,19 +233,29 @@ public String toString() {
 	 */
 	@Override
 	public boolean equals(Object obj) {
+		
 	    if (obj != null && obj instanceof FDTMC) {
 	        FDTMC other = (FDTMC) obj;
 	        LinkedList<List<Interface>> thisInterfaces = new LinkedList<List<Interface>>(interfaces.values());
             LinkedList<List<Interface>> otherInterfaces = new LinkedList<List<Interface>>(other.interfaces.values());
-            return states.equals(other.states)
-	                && getInitialState().equals(other.getInitialState())
-	                && getSuccessState().equals(other.getSuccessState())
-	                && getErrorState().equals(other.getErrorState())
-	                && transitionSystem.equals(other.transitionSystem)
-	                && thisInterfaces.equals(otherInterfaces);
+            
+            return compareState(other, thisInterfaces, otherInterfaces);
 	    }
+	    
 	    return false;
 	}
+	
+	private boolean compareState(FDTMC other, LinkedList<List<Interface>> thisInterfaces, LinkedList<List<Interface>> otherInterfaces) {
+		
+		boolean state = states.equals(other.states)
+                && getInitialState().equals(other.getInitialState())
+                && getSuccessState().equals(other.getSuccessState())
+                && getErrorState().equals(other.getErrorState())
+                && transitionSystem.equals(other.transitionSystem)
+                && thisInterfaces.equals(otherInterfaces);
+		
+		return state;
+	}
 
 	@Override
     public int hashCode() {
diff --git a/src/fdtmc/Interface.java b/src/fdtmc/Interface.java
index f6cd969..b077388 100644
--- a/src/fdtmc/Interface.java
+++ b/src/fdtmc/Interface.java
@@ -53,15 +53,19 @@ public String getAbstractedId() {
     public boolean equals(Object obj) {
         if (obj != null && obj instanceof Interface) {
             Interface other = (Interface) obj;
-            return initial.equals(other.initial)
-                    && success.equals(other.success)
-                    && error.equals(other.error)
-                    && successTransition.equals(other.successTransition)
-                    && errorTransition.equals(other.errorTransition);
+            return compareAllAtributtes(other);
         }
         return false;
     }
 
+	private boolean compareAllAtributtes(Interface other) {
+		return initial.equals(other.initial)
+		        && success.equals(other.success)
+		        && error.equals(other.error)
+		        && successTransition.equals(other.successTransition)
+		        && errorTransition.equals(other.errorTransition);
+	}
+
     @Override
     public int hashCode() {
         return initial.hashCode()
diff --git a/src/tool/RDGNode.java b/src/tool/RDGNode.java
index 180097c..bcf333f 100644
--- a/src/tool/RDGNode.java
+++ b/src/tool/RDGNode.java
@@ -90,7 +90,9 @@ public static RDGNode getById(String id) {
     }
 
     public static String getNextId() {
-        return "n" + lastNodeIndex++;
+        String nextId;
+        nextId = "n" + lastNodeIndex++;
+        return nextId;
     }
 
     /**
@@ -102,21 +104,29 @@ public static String getNextId() {
     public boolean equals(Object obj) {
         if (obj != null && obj instanceof RDGNode) {
             RDGNode other = (RDGNode) obj;
-            return this.getPresenceCondition().equals(other.getPresenceCondition())
-                    && this.getFDTMC().equals(other.getFDTMC())
-                    && this.getDependencies().equals(other.getDependencies());
+            return compareAttributesOfRDGNodeObject(other);
         }
         return false;
     }
 
+	private boolean compareAttributesOfRDGNodeObject(RDGNode other) {
+		return this.getPresenceCondition().equals(other.getPresenceCondition())
+		        && this.getFDTMC().equals(other.getFDTMC())
+		        && this.getDependencies().equals(other.getDependencies());
+	}
+
     @Override
     public int hashCode() {
-        return id.hashCode() + presenceCondition.hashCode() + fdtmc.hashCode() + dependencies.hashCode();
+        int hashCode;
+        hashCode = id.hashCode() + presenceCondition.hashCode() + fdtmc.hashCode() + dependencies.hashCode();
+        return hashCode;
     }
 
     @Override
     public String toString() {
-        return getId() + " (" + getPresenceCondition() + ")";
+        String newString;
+        newString = getId() + " (" + getPresenceCondition() + ")";
+        return newString;
     }
 
     /**