diff --git a/.idea/.gitignore b/.idea/.gitignore
new file mode 100644
index 0000000..ab1f416
--- /dev/null
+++ b/.idea/.gitignore
@@ -0,0 +1,10 @@
+# Default ignored files
+/shelf/
+/workspace.xml
+# Ignored default folder with query files
+/queries/
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml
+# Editor-based HTTP Client requests
+/httpRequests/
diff --git a/.idea/compiler.xml b/.idea/compiler.xml
new file mode 100644
index 0000000..812c3f9
--- /dev/null
+++ b/.idea/compiler.xml
@@ -0,0 +1,13 @@
+
+
+
+
+
+
+
+
+
+
+
+
+
\ No newline at end of file
diff --git a/.idea/encodings.xml b/.idea/encodings.xml
new file mode 100644
index 0000000..aa00ffa
--- /dev/null
+++ b/.idea/encodings.xml
@@ -0,0 +1,7 @@
+
+
+
+
+
+
+
\ No newline at end of file
diff --git a/.idea/jarRepositories.xml b/.idea/jarRepositories.xml
new file mode 100644
index 0000000..105dbd3
--- /dev/null
+++ b/.idea/jarRepositories.xml
@@ -0,0 +1,20 @@
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
\ No newline at end of file
diff --git a/.idea/misc.xml b/.idea/misc.xml
new file mode 100644
index 0000000..4f9985e
--- /dev/null
+++ b/.idea/misc.xml
@@ -0,0 +1,12 @@
+
+
+
+
+
+
+
+
\ No newline at end of file
diff --git a/.idea/vcs.xml b/.idea/vcs.xml
new file mode 100644
index 0000000..35eb1dd
--- /dev/null
+++ b/.idea/vcs.xml
@@ -0,0 +1,6 @@
+
+
+
+
+
+
\ No newline at end of file
diff --git a/pom.xml b/pom.xml
index 33ea6f3..0f704db 100644
--- a/pom.xml
+++ b/pom.xml
@@ -9,8 +9,8 @@
1.0-SNAPSHOT
- 23
- 23
+ 21
+ 21
UTF-8
diff --git a/src/main/java/dev/banking/model/BankAccount.java b/src/main/java/dev/banking/model/BankAccount.java
index 745ede2..2e7260f 100644
--- a/src/main/java/dev/banking/model/BankAccount.java
+++ b/src/main/java/dev/banking/model/BankAccount.java
@@ -1,18 +1,15 @@
package dev.banking.model;
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+
public class BankAccount {
private final int accountId;
private long balance;
+ private final ReadWriteLock lock = new ReentrantReadWriteLock();
- /*
- * Students may introduce additional fields
- * such as:
- * - Lock / ReentrantLock
- * - ReadWriteLock
- * - Object monitor
- * - etc.
- */
public BankAccount(int accountId, long initialBalance) {
this.accountId = accountId;
@@ -23,40 +20,36 @@ public class BankAccount {
return accountId;
}
- /*
- * TODO:
- * Return the current balance in a thread-safe way.
- *
- * Requirements:
- * - Must be safe under concurrent reads/writes
- * - Should not block unnecessarily if using read/write locks
- */
+
public long getBalance() {
- throw new UnsupportedOperationException("TODO: implement thread-safe balance read");
+ lock.readLock().lock();
+ try {
+ return balance;
+ }
+ finally {
+ lock.readLock().unlock();
+ }
}
- /*
- * TODO:
- * Increase balance atomically.
- *
- * Requirements:
- * - Must not lose updates under concurrency
- */
+
public void deposit(long amount) {
- throw new UnsupportedOperationException("TODO: implement thread-safe deposit");
+ lock.writeLock().lock();
+ try {
+ balance += amount;
+ }
+ finally {
+ lock.writeLock().unlock();
+ }
}
- /*
- * TODO:
- * Decrease balance atomically.
- *
- * Requirements:
- * - Must not cause race conditions
- * - Negative balance handling is NOT required unless you decide
- * to extend the system (optional)
- */
public void withdraw(long amount) {
- throw new UnsupportedOperationException("TODO: implement thread-safe withdraw");
+ lock.writeLock().lock();
+ try {
+ balance -= amount;
+ }
+ finally {
+ lock.writeLock().unlock();
+ }
}
/*
@@ -73,6 +66,21 @@ public class BankAccount {
* - Or tryLock with retry strategy
*/
public void transfer(BankAccount target, long amount) {
- throw new UnsupportedOperationException("TODO: implement atomic deadlock-free transfer");
+ BankAccount first = this.accountId < target.accountId ? this : target;
+ BankAccount second = this.accountId > target.accountId ? this : target;
+
+ first.lock.writeLock().lock();
+ try {
+ second.lock.writeLock().lock();
+ try {
+ this.balance -= amount;
+ target.balance += amount;
+ } finally {
+ second.lock.writeLock().unlock();
+ }
+ }
+ finally{
+ first.lock.writeLock().unlock();
+ }
}
}
\ No newline at end of file