What is the use of synchronizations?
Every object has a lock, when a synchronized keyword is used on a piece of code the, lock must be obtained by the thread first to execute that code, other threads will not be allowed to execute that piece of code till this lock is released. 33. How could Java classes direct program messages to the system console, but error messages, say to a file? A. The class System has a variable out that represents the standard output, and the variable err that represent the standard error device. By default, they both point at the system console. This how the standard output could be re-directed: Stream st = new Stream(new FileOutputStream(“output.txt”)); System.setErr(st); System.setOut(st); 34. What’s the difference between an interface and an abstract class? A. An abstract class may contain code in method bodies, which is not allowed in an interface. With abstract classes, you have to inherit your class from it and Java does not allow multiple inheritance. On the other hand, you can implement mu
