dodatkowa klasa do ewentualnego nadpisywania

src/main/java/Overwrite.java

@@ -0,0 +1,21 @@
+import java.io.*;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.util.ArrayList;
+import java.util.List;
+
+public class Overwrite {
+    public static void checkIfPeselExists(File file, String firstName, String lastName, String Pesel) {
+        if(file.exists()) {
+            try {
+                List<String> fileContent = new ArrayList<>(Files.readAllLines(file.toPath(), StandardCharsets.UTF_8));
+            } catch (IOException ex) {
+                System.out.println(ex.getMessage());
+            }
+
+
+        } else {
+            System.out.println("Problem z odczytaniem danych z pliku.");
+        }
+    }
+}

src/main/java/Read.java

@@ -25,7 +25,9 @@ public class Read {
             }
             else {
                 boolean saved = false;
-                // sprawdzenie czy już siedzi w pliku
+
+                Overwrite.checkIfPeselExists(file, personalInfo.get(1), personalInfo.get(2), personalInfo.get(3));
+
                 if(!saved) {
                     Write.write(personalInfo, file);
                     System.out.println("Osoba dodana do listy.");

src/main/java/Write.java

@@ -2,23 +2,6 @@ import java.io.*;
 import java.util.List;
 
 public class Write {
-    public static void checkIfPeselExists(File file, List data) {
-        if(file.exists()) {
-            try (BufferedReader bufferedReader = new BufferedReader(new FileReader(file))) {
-                String line;
-                while((line = bufferedReader.readLine()) != null) {
-                    //
-                }
-            } catch (FileNotFoundException e) {
-                e.printStackTrace();
-            } catch (IOException e) {
-                e.printStackTrace();
-            }
-        } else {
-            System.out.println("Problem z odczytaniem danych z pliku.");
-        }
-    }
-
     public static void write(List data, File file) {
         if(file.exists()) {
             try (BufferedWriter fileWriter = new BufferedWriter(new FileWriter(file, true))){