diff --git a/src/org/ntlab/deltaViewer/CollaborationViewer.java b/src/org/ntlab/deltaViewer/CollaborationViewer.java
index 3fc4a99..1150557 100644
--- a/src/org/ntlab/deltaViewer/CollaborationViewer.java
+++ b/src/org/ntlab/deltaViewer/CollaborationViewer.java
@@ -523,25 +523,37 @@
 			
 			// Search for objectReference srcClassName, fieldName between curAlias and nexAlias.
 			if (curAlias.getAliasType() == AliasType.THIS) {
+				Statement statement = nextAlias.getOccurrencePoint().getStatement();
 				if (nextAlias.getAliasType() == AliasType.RETURN_VALUE) {
 					MethodExecution nextMethodExec = nextAlias.getMethodExecution();
 					//Array��List�̂Ƃ��������x����t����i�m���ɕ������Ă�����̂Ƃ�)getSignature->contains("List.get(") || "Map.get(") <�z���C�g���X�g>
-					if (nextMethodExec.getSignature().contains("List.get(") ||
-							nextMethodExec.getSignature().contains("Map.get(")) {
+					if (nextMethodExec.getSignature().contains("List.get(")) {
 						srcClassName = nextMethodExec.getThisClassName();
 						fieldName = nextMethodExec.getArguments().get(0).getId();
 						System.out.println("rTHIS " + srcClassName + ", " + nextMethodExec.getArguments().get(0).getId());
+					} else if (nextMethodExec.getSignature().contains("Map.get(")) {
+						srcClassName = nextMethodExec.getThisClassName();
+						fieldName = "";
+						System.out.println("rTHIS " + srcClassName + ", " + nextMethodExec.getArguments().get(0).getId());						
 					}
 				} else {
-					Statement statement = nextAlias.getOccurrencePoint().getStatement();
-					if(statement instanceof FieldAccess && curAliasObjId.equals(((FieldAccess)statement).getContainerObjId())) {
-						if (((FieldAccess)statement).getFieldName() != null) {
-							String fieldNames[] = formatFieldName(((FieldAccess)statement).getFieldName());
+					if (nextAlias.getAliasType() == AliasType.FIELD) { // When final local.
+						if (statement != null && statement instanceof MethodInvocation && curAliasObjId.equals(((MethodInvocation)statement).getThisObjId())) {						
+							MethodInvocation methodInvocation = (MethodInvocation)statement;
+							srcClassName = methodInvocation.getThisClassName();
+							fieldName = nextAliasObjId;
+						}
+					}
+					if(statement != null && statement instanceof FieldAccess 
+							&& curAliasObjId.equals(((FieldAccess)statement).getContainerObjId())) { // Contains alias type of nextAlias is FIELD.
+						FieldAccess fieldAccess = (FieldAccess)statement;
+						if (fieldAccess.getFieldName() != null) {
+							String fieldNames[] = formatFieldName(fieldAccess.getFieldName());
 							srcClassName = fieldNames[0];
 							fieldName = fieldNames[1];
 						} else {
-							srcClassName = ((FieldAccess)statement).getContainerClassName();
-							fieldName = "";
+							srcClassName = fieldAccess.getContainerClassName();
+							fieldName = nextAliasObjId;
 						}
 					}
 				}
@@ -577,8 +589,13 @@
 					Object dstCell = objectToVertexMap.get(nextAliasObjId).getCell();
 					if (srcCell != null && dstCell != null) { // isCreation()
 						System.out.println("makeEdgeObject: " + fieldName + ", " + srcClassName + " (" + srcCell.hashCode() + "), " + " (" + dstCell.hashCode() + ")"/* + ", " + dstClassName*/);
-						// BUG:NullPointerException
-						Object edge = mxgraph.insertDeltaEdge(getMxDefaultParent(), fieldName, fieldName, srcCell, dstCell);
+						// TODO: Fix bug of NullPointerException.
+						mxICell edge = null;
+						if (fieldName.equals(nextAliasObjId)) { // If fieldName is objectId.
+							edge = (mxICell) mxgraph.insertDeltaEdge(getMxDefaultParent(), "", "", srcCell, dstCell);							
+						} else {
+							edge = (mxICell) mxgraph.insertDeltaEdge(getMxDefaultParent(), fieldName, fieldName, srcCell, dstCell);
+						}
 						Point2D absPtSrcCell = getAbsolutePointforCell((mxICell)srcCell);
 						Point2D absPtDstCell = getAbsolutePointforCell((mxICell)dstCell);
 						setEdgePoint((mxICell)edge, absPtSrcCell, absPtDstCell);