1. How the Observer and Observable used in Java Programming?
Objects that subclass the Observable class maintain a list of observers. When an Observable object is updated it invokes the update() method of each of its observers to notify the observers that it has changed state. The Observer interface is implemented by objects that observe Observable objects.
2. Described about synchronization and why is it important in Java Programming?
With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchronization, it is possible for one thread to modify a shared object while another thread is in the process of using or updating that object's value. This often causes dirty data and leads to significant errors.
3. What are synchronized methods and tell me about the synchronized statements in Java Programming?
Synchronized methods are methods that are used to control access to an object. A thread only executes a synchronized method after it has acquired the lock for the method's object or class. Synchronized statements are similar to synchronized methods. A synchronized statement can only be executed after a thread has acquired the lock for the object or class referenced in the synchronized statement.
4. Which three ways in which thread can enter the waiting state in Java Programming?
A thread can enter the waiting state by invoking its sleep() method, by blocking on I/O, by unsuccessfully attempting to acquire an object's lock, or by invoking an object's wait() method. It can also enter the waiting state by invoking its (deprecated) suspend() method.
5. Can lock be acquired on a class in Java Programming?
Yes, a lock can be acquired on a class. This lock is acquired on the class's Class object.
6. What is new with the stop(), suspend() and resume() methods in JDK 1.2?
The stop(), suspend() and resume() methods have been deprecated in JDK 1.2.
7. What is preferred size of a component in Java Programming?
The preferred size of a component is the minimum component size that will allow the component to display normally.
8. Which containers use the FlowLayout as their default layout in Java Programming?
The Panel and Applet classes use the FlowLayout as their default layout.
9. Which method is used to specify container's layout in Java Programming?
The setLayout() method is used to specify a container's layout in Java Programming.
10. Described the Collections API in Java Programming?
The Collections API is a set of classes and interfaces that support operations on collections of objects.
11. Which containers use border layout as their default layout?
The window, Frame and Dialog classes use a border layout as their default layout in Java Programming.
12. How Java handle integer overflows and underflows?
It uses those low order bytes of the result that can fit into the size of the type allowed by the operation.
13. Described the list interface in Java Programming?
The List interface provides support for ordered collections of objects.
14. Which state does thread enter when it terminates its processing in Java Programming?
When a thread terminates its processing, it enters the dead state.
15. Suppose if method is declared as protected, where may method be accessed in Java Programming?
A protected method may only be accessed by classes or interfaces of the same package or by subclasses of the class in which it is declared.
16. Define Vector class in Java Programming?
The Vector class in Java Programming provides the capability to implement a growable array of objects.
Unicode requires 16 bits and ASCII require 7 bits. Although the ASCII character set uses only 7 bits, it is usually represented as 8 bits. UTF-8 represents characters using 8, 16, and 18 bit patterns. UTF-16 uses 16-bit and larger bit patterns.
A (non-local) inner class may be declared as public, protected, private, static, final, or abstract.
19. Explain the difference between yielding and sleeping in Java Programming?
When a task invokes its yield() method, it returns to the ready state. When a task invokes its sleep() method, it returns to the waiting state.
20. Define transient variable?
A transient variable is a variable that may not be serialized.
21. Define wrapped classes in Java Programming?
Wrapped classes are classes that allow primitive types to be accessed as objects.
22. Is the size of keyword in Java Programming?
The sizeof operator is not a keyword in Java Programming.
23. Described about native method in Java Programming?
A native method is a method that is implemented in a language other than Java.
24. How to write loop indefinitely in Java Programming?
for(;;)-for loop; while(true)-always true, etc.
25. Name the component subclasses that support painting in Java Programming?
The Canvas, Frame, Panel, and Applet classes support painting.
