TheWellGroundedJavaDeveloper: FSOAccouunt, FSOMain(Concurrency)

the-well-grounded-java-developer/src/main/java/com/currenjin/concurrency/FSOAccount.java

@@ -0,0 +1,33 @@
+package com.currenjin.concurrency;
+
+public class FSOAccount {
+    private double balance;
+
+    public FSOAccount(double openingBalance) {
+        this.balance = openingBalance;
+    }
+
+    public synchronized void deposit(int amount) {
+        balance += amount;
+    }
+
+    public double getBalance() {
+        return balance;
+    }
+
+    public synchronized boolean transferTo(FSOAccount other, int amount) {
+        try {
+            Thread.sleep(10);
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+        }
+
+        if (amount >= balance) {
+            balance -= amount;
+            other.deposit(amount);
+            return true;
+        }
+
+        return false;
+    }
+}

the-well-grounded-java-developer/src/main/java/com/currenjin/concurrency/FSOMain.java

@@ -0,0 +1,35 @@
+package com.currenjin.concurrency;
+
+public class FSOMain {
+    private static final int MAX_TRANSFERS = 1_000;
+
+    public static void main(String[] args) throws InterruptedException {
+        FSOAccount a = new FSOAccount(10_000);
+        FSOAccount b = new FSOAccount(10_000);
+
+        Thread tA = new Thread(() -> {
+            for (int i = 0; i < MAX_TRANSFERS; i++) {
+                boolean ok = a.transferTo(b, 1);
+                if (!ok) {
+                    System.out.println("Thread A failed at " + i);
+                }
+            }
+        });
+
+        Thread tB = new Thread(() -> {
+            for (int i = 0; i < MAX_TRANSFERS; i++) {
+                boolean ok = b.transferTo(a, 1);
+                if (!ok) {
+                    System.out.println("Thread B failed at " + i);
+                }
+            }
+        });
+
+        tA.start();
+        tB.start();
+        tA.join();
+        tB.join();
+
+        System.out.println("End: " + a.getBalance() + " : " + b.getBalance());
+    }
+}