import java.util.ArrayList;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.UUID;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class Test {
Set<Thread> orderingThreads = new HashSet<Thread>();
Lock lock = new ReentrantLock();
final Map<String, Integer> inventoryMap = new LinkedHashMap<String, Integer>();
List<Task> customerOrders = new ArrayList<Task>();
public static void main(String[] args) throws InterruptedException {
Test t = new Test();
t.start();
}
private void start() throws InterruptedException {
for (int i = 0; i < 10; i++) {
inventoryMap.put("Book #" + i, 100);
}
for (int i = 0; i < 20; i++) {
createOrderingThread();
}
checkInventoryLevels();
for (Thread thread : orderingThreads) {
thread.interrupt();
}
displayOrders();
}
private void displayOrders() {
try {
lock.lock();
for (Task order : customerOrders) {
System.out.println(order.getCount() + " "
+ order.id() + " for " + order.getTaskName());
}
} finally {
lock.unlock();
}
}
private void createOrderingThread() {
Thread orderingThread = new Thread(new Runnable() {
public void run() {
while (!Thread.interrupted()) {
createRandomOrder();
}
}
});
orderingThread.start();
orderingThreads.add(orderingThread);
}
private void createRandomOrder() {
String itemOrdered = UUID.randomUUID().toString();
String customerName = "Customer ";
fulfillOrder(itemOrdered, 2, customerName);
}
private boolean fulfillOrder(String itemOrdered, int quantityOrdered,
String customerName) {
try {
lock.lock();
int currentInventory = inventoryMap.get(itemOrdered);
if (currentInventory < quantityOrdered) {
return false;
}
inventoryMap.put(itemOrdered, currentInventory - quantityOrdered);
Task order = new Task(itemOrdered, quantityOrdered,
customerName);
customerOrders.add(order);
return true;
} finally {
lock.unlock();
}
}
private void checkInventoryLevels() {
try {
lock.lock();
for (Map.Entry<String, Integer> inventoryEntry : inventoryMap.entrySet()) {
System.out.println(inventoryEntry.getKey() + " "
+ inventoryEntry.getValue());
}
} finally {
lock.unlock();
}
}
}
class Task {
String id;
int count;
String taskName;
Task(String id, int q, String c) {
this.id = id;
this.count = q;
this.taskName = c;
}
public String id() {
return id;
}
public int getCount() {
return count;
}
public String getTaskName() {
return taskName;
}
}
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