diff --git a/src/exercicses/ex_f/Account.java b/src/exercicses/ex_f/Account.java
new file mode 100644
index 0000000..29377ba
--- /dev/null
+++ b/src/exercicses/ex_f/Account.java
@@ -0,0 +1,17 @@
+package exercicses.ex_f;
+
+public class Account {
+    private int balance;
+
+    public synchronized void withdraw(int amount) {
+        balance -= amount;
+    }
+
+    public synchronized void deposit(int amount) {
+        balance += amount;
+    }
+
+    public synchronized int getBalance() {
+        return balance;
+    }
+}
\ No newline at end of file
diff --git a/src/exercicses/ex_f/Customer.java b/src/exercicses/ex_f/Customer.java
new file mode 100644
index 0000000..fa82f6c
--- /dev/null
+++ b/src/exercicses/ex_f/Customer.java
@@ -0,0 +1,26 @@
+package exercicses.ex_f;
+
+public class Customer implements Runnable {
+    private String name;
+    private Account account;
+
+    public Customer(String name, Account account) {
+        this.name = name;
+        this.account = account;
+    }
+
+    @Override
+    public void run() {
+        while (true) {
+            account.deposit((int) (Math.random() * 1000));
+            System.out.println(name + " has deposited money on account with new balance " + account.getBalance());
+            account.withdraw((int) (Math.random() * 1000));
+            System.out.println(name + " has withdrawn money from the account with new balance " + account.getBalance());
+            try {
+                Thread.sleep(100);
+            } catch (InterruptedException e) {
+                throw new RuntimeException(e);
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/exercicses/ex_f/TestingThreadInterferences.java b/src/exercicses/ex_f/TestingThreadInterferences.java
new file mode 100644
index 0000000..d6edf05
--- /dev/null
+++ b/src/exercicses/ex_f/TestingThreadInterferences.java
@@ -0,0 +1,10 @@
+package exercicses.ex_f;
+
+public class TestingThreadInterferences {
+    public static void main(String[] args) {
+        // shared account object
+        Account account = new Account();
+        (new Thread(new Customer("Damien", account))).start();
+        (new Thread(new Customer("Hélène", account))).start();
+    }
+}
\ No newline at end of file