jgwest

class CustomerDb2 {

	private final List<Customers> customers = new ArrayList<>();

	private void addCustomer(Customer c) {
		synchronized(customers) {
			customers.add(c);
		}
	}

jgwest

SharedThreadContext threadContext = {...}

final YourProtectedData[] ypd = new YourProtectedData[1];
threadContext.own(stc -> {
		YourProtectedData innerYpd = stc.getProtectedData();
		ypd[0] = innerYpd;

}, logContext);

ypd[0].incrementSomeData(); // FAILS with exception: An attempt was made (...)

jgwest

SharedThreadContext stc = {...};

YourProtectedData ypd = stc.getProtectedData();  // FAILS with exception: An attempt was made to call a method in shared context without owning the required lock.

jgwest

Integer someData = 10;

SharedThreadContext threadContext = new SharedThreadContext(someData);

threadContext.own(stc -> {
		YourProtectedData ypd = stc.getProtectedData();
		int newValue = ypd.incrementSomeData();
		System.out.println("New value is "+newValue);
}, logContext);

jgwest

public class SharedThreadContext {
	private final ReentrantLock lock = new ReentrantLock(); 

	// private data to protect, as private fields of SharedThreadContext
	private final YourProtectedData yourProtectedData1; 

	public SharedThreadContext(Integer ypdData) {
		this.yourProtectedData1 = new YourProtectedData(ypdData);
	}

jgwest

class CustomerDb3 {

	private final List<Customers> customers = new ArrayList<>();

	private void countOrders(Customer c) {
		List<Order> orders;
		synchronized(c) {
			orders = c.getOrder();
		}

jgwest

class CustomerDb {

	List<Customers> customers = new ArrayList<>();

	synchronized List<Customers> getCustomers() {
		return customers;
	}
}

class CustomerUpdater {

jgwest

class Customer {
	String name;
	List<Order> orders = new ArrayList<>(); 

	//	getters / setters for above.
}