implemented AircraftRepository methods

src/main/java/hs/fulda/de/ci/exam/project/AircraftRepository.java

@@ -0,0 +1,31 @@
+package hs.fulda.de.ci.exam.project;
+
+import java.io.*;
+import java.util.Scanner;
+
+public class AircraftRepository {
+
+    boolean save(Aircraft aircraft) throws IOException {
+            FileWriter fw = new FileWriter("aircraft_list.txt", true);
+            BufferedWriter bw = new BufferedWriter(fw);
+            bw.write(aircraft.toString());
+            bw.newLine();
+            bw.close();
+            return true;
+        };
+        String findAircraftByAircraftNumber(String AircraftName){
+            File file = new File("aircraft_list.txt");
+            try {
+                Scanner scanner = new Scanner(file);
+                while (scanner.hasNextLine()) {
+                    String line = scanner.nextLine();
+                    if(line.matches("(.*)"+AircraftName+"(.*)")) {
+                        return line;
+                    }
+                }
+            } catch(FileNotFoundException e) {
+                System.out.println("There are no aircrafts added yet. Please add a aircraft first");
+            }
+            return "";
+        }
+}