added function for closing file to WriterActiveObject

src/main/java/de/dhbwstuttgart/typeinference/unify/WriterActiveObject.java

@@ -12,10 +12,21 @@ public class WriterActiveObject {
         this.writer = writer;
     }
 
+    public void close(){
+        pool.execute(()->{
+            try {
+                writer.close();
+            } catch (IOException e) {
+                System.out.println(e.getMessage());
+            }
+        });
+    }
+
     public void write(String message){
         pool.execute(()->{
             try {
                 writer.write(message);
+                writer.flush();
             } catch (IOException e) {
                 System.out.println(e.getMessage());
             }