diff --git a/src/main/java/org/Main.java b/src/main/java/org/Main.java
new file mode 100644
index 0000000..4999d5a
--- /dev/null
+++ b/src/main/java/org/Main.java
@@ -0,0 +1,7 @@
+package org;
+
+public class Main {
+    public static void main(String[] args) {
+
+    }
+}
diff --git a/src/main/java/org/exceptions/FileService.java b/src/main/java/org/exceptions/FileService.java
new file mode 100644
index 0000000..e2ab949
--- /dev/null
+++ b/src/main/java/org/exceptions/FileService.java
@@ -0,0 +1,86 @@
+package org.exceptions;
+
+import java.io.BufferedReader;
+import java.io.BufferedWriter;
+import java.io.FileReader;
+import java.io.FileWriter;
+import java.text.SimpleDateFormat;
+import java.util.Date;
+import java.util.Scanner;
+
+public class FileService {
+
+
+    public static void main(String[] args) {
+
+        Scanner scanner = new Scanner(System.in);
+
+        System.out.println("Enter you first name: ");
+        String firstName = scanner.nextLine();
+
+        System.out.println("Enter you last name: ");
+        String lastName = scanner.nextLine();
+
+        System.out.println("Enter your national code: ");
+        Long nationalCode = scanner.nextLong();
+        scanner.nextLine();
+
+        System.out.println("Enter your email: ");
+        String email = scanner.nextLine();
+
+        System.out.println("Enter your phone number: ");
+        Long phoneNumber = scanner.nextLong();
+        scanner.nextLine();
+
+        System.out.println("Enter your dateOfBirth: ");
+        String dateOfBirth = scanner.nextLine();
+
+        UserEntity user = null;
+
+        user = new UserEntity(firstName, lastName, nationalCode, email, phoneNumber, parseDate(dateOfBirth));
+
+        System.out.println(user.toString());
+
+        System.out.println(writeFile(user));
+        readFile();
+
+
+    }
+
+
+    public static String writeFile(UserEntity user) {
+
+        FileWriter fw = new FileWriter("D:\\ExceptionHandling\\userInformation.txt", true);
+        BufferedWriter bw = new BufferedWriter(fw);
+
+        bw.write(user.toString());
+        bw.close();
+        return "user information written to file";
+    }
+
+
+    public static void readFile() {
+
+        FileReader file = new FileReader("D:\\ExceptionHandling\\userInformation.txt");
+
+        BufferedReader fileInput = new BufferedReader(file);
+
+        for (int counter = 0; counter < 3; counter++)
+            System.out.println(fileInput.readLine());
+
+        fileInput.close();
+    }
+
+
+    public static Date parseDate(String date) {
+        SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
+
+        Date dob = null;
+
+        dob = formatter.parse(date);
+
+
+        return dob;
+    }
+
+}
diff --git a/src/main/java/org/exceptions/Unknown.java b/src/main/java/org/exceptions/Unknown.java
new file mode 100644
index 0000000..57a0aba
--- /dev/null
+++ b/src/main/java/org/exceptions/Unknown.java
@@ -0,0 +1,62 @@
+package org.exceptions;
+
+import java.util.regex.Pattern;
+
+public class Unknown {
+    public static void main(String[] args) {
+
+        UserEntity user = new UserEntity("Ali", "Ahmadi", 1234567890L,
+                null, 989111111111L, null);
+
+        validateEmail(user);
+        calculatePayment(5000, 0);
+        convertUserAge("twenty");
+        completeRegistration(user);
+
+    }
+
+
+    //nullPointerException
+    //IllegalArgumentException
+    public static void validateEmail(UserEntity user) {
+
+        String email = user.getEmail();
+
+        String emailRegex = "^[A-Za-z0-9+_.-]+@[A-Za-z0-9.-]+$";
+
+        if (!Pattern.matches(emailRegex, email)) {
+            throw new IllegalArgumentException("Invalid email format");
+        }
+
+        System.out.println("User email is valid");
+    }
+
+    // ArithmeticException
+    public static void calculatePayment(int totalAmount, int installmentCount) {
+
+        int payment = totalAmount / installmentCount;
+
+        System.out.println("Each installment : " + payment);
+    }
+
+    // NumberFormatException
+    public static void convertUserAge(String ageInput) {
+
+        int age = Integer.parseInt(ageInput);
+
+        System.out.println("User age: " + age);
+    }
+
+//    IllegalStateException
+    public static void completeRegistration(UserEntity user) {
+
+        if (user.getDateOfBirth() == null) {
+            throw new IllegalStateException(
+                    "Registration cannot be completed. Date of birth is missing."
+            );
+        }
+
+        System.out.println("Registration completed");
+    }
+
+}
\ No newline at end of file
diff --git a/src/main/java/org/exceptions/UserEntity.java b/src/main/java/org/exceptions/UserEntity.java
new file mode 100644
index 0000000..077f72f
--- /dev/null
+++ b/src/main/java/org/exceptions/UserEntity.java
@@ -0,0 +1,84 @@
+package org.exceptions;
+
+import java.util.Date;
+
+public class UserEntity {
+
+    private String firstName;
+    private String lastName;
+    private Long nationalCode;
+    private String email;
+    private Long phoneNumber;
+    private Date dateOfBirth;
+
+
+    public UserEntity(String firstName, String lastName, Long nationalCode, String email, Long phoneNumber, Date dateOfBirth) {
+        this.firstName = firstName;
+        this.lastName = lastName;
+        this.nationalCode = nationalCode;
+        this.email = email;
+        this.phoneNumber = phoneNumber;
+        this.dateOfBirth = dateOfBirth;
+    }
+
+
+    public String getFirstName() {
+        return firstName;
+    }
+
+    public void setFirstName(String firstName) {
+        this.firstName = firstName;
+    }
+
+    public String getLastName() {
+        return lastName;
+    }
+
+    public void setLastName(String lastName) {
+        this.lastName = lastName;
+    }
+
+    public Long getNationalCode() {
+        return nationalCode;
+    }
+
+    public void setNationalCode(Long nationalCode) {
+        this.nationalCode = nationalCode;
+    }
+
+    public String getEmail() {
+        return email;
+    }
+
+    public void setEmail(String email) {
+        this.email = email;
+    }
+
+    public Long getPhoneNumber() {
+        return phoneNumber;
+    }
+
+    public void setPhoneNumber(Long phoneNumber) {
+        this.phoneNumber = phoneNumber;
+    }
+
+    public Date getDateOfBirth() {
+        return dateOfBirth;
+    }
+
+    public void setDateOfBirth(Date dateOfBirth) {
+        this.dateOfBirth = dateOfBirth;
+    }
+
+    @Override
+    public String toString() {
+        return "UserEntity{" +
+                "firstName='" + firstName + '\'' +
+                ", lastName='" + lastName + '\'' +
+                ", nationalCode=" + nationalCode +
+                ", email='" + email + '\'' +
+                ", phoneNumber=" + phoneNumber +
+                ", dateOfBirth=" + dateOfBirth +
+                '}';
+    }
+}
diff --git a/userInformation.txt b/userInformation.txt
new file mode 100644
index 0000000..e69de29