Java Confinement

confinement.java

// MyClass.property is confined. may only be get or set on the main thread.
// Wo the `property` member is not thread-safe, but the code 
// overall *is* thread safe if you confine access to `property` to the main thread only

public class MyClass {
    private Object property;
    
    public void action() {
        assert isMainThread();
    
        doInBackground({
            assert !isMainThread();
            Object result = doWork();
        
            doOnMainThread({
                assert isMainThread();
                this.property = result;
            });
        
        });
    }
}