ref tells the compiler that the object is initialized before entering the function, while out tells the compiler that the object will be initialized inside the function. So while ref is two-ways, out is out-only.
The synchronized keyword is all about different threads reading and writing to the same variables, objects and resources. This is not a trivial topic in Java, but here is a quote from Sun: synchronized methods enable a simple strategy for preventing thread interference and memory consistency errors: if an object is visible to more than … Read more
If you’re in the global scope then there’s not much difference. Read Kangax’s answer for explanation If you’re in a function then var will create a local variable, “no var” will look up the scope chain until it finds the variable or hits the global scope (at which point it will create it): // These … Read more