1. Is Java a super set of JavaScript?
No. They are completely different. Some syntax may be similar.
2. What is the purpose of the enableEvents() method in Java Programming?
The enableEvents() method is used to enable an event for a particular object. Normally, an event is enabled when a listener is added to an object for a particular event. The enableEvents() method is used by objects that handle events by overriding their event-dispatch methods.
3. What is the Set interface in Java Programming?
The Set interface provides methods for accessing the elements of a finite mathematical set. Sets do not allow duplicate elements.
4. What an I/O filter in Java Programming?
An I/O filter is an object that reads from one stream and writes to another, usually altering the data in some way as it is passed from one stream to another.
The == operator compares two objects to determine if they are the same object in memory. It is possible for two String objects to have the same value, but located indifferent areas of memory.
6. How are this() and super() used with constructors in Java Programming?
this() is used to invoke a constructor of the same class. super() is used to invoke a superclass constructor in Java Programming.
7. What class allows you to read objects directly from a stream in Java Programming?
The ObjectInputStream class supports the reading of objects from input streams.
8. Name Container classes in Java Programming?
Container classes in Java:
Window,
Frame,
Dialog,
FileDialog,
Panel,
Applet,
or ScrollPane
9. What is casting in Java Programming?
There are two types of casting, casting between primitive numeric types and casting between object references. Casting between numeric types is used to convert larger values, such as double values, to smaller values, such as byte values. Casting between object references is used to refer to an object by a compatible class, interface, or array type reference.
10. What restrictions are placed on method overriding in Java Programming?
Overridden methods must have the same name, argument list, and return type. The overriding method may not limit the access of the method it overrides. The overriding method may not throw any exceptions that may not be thrown by the overridden method.
11. What restrictions are placed on method overloading in Java Programming?
Two methods may not have the same name and argument list but different return types.
12. How does multithreading take place on a computer with a single CPU in Java Programming?
The operating system's task scheduler allocates execution time to multiple tasks. By quickly switching between executing tasks, it creates the impression that tasks execute sequentially.
13. What is the purpose of the File class in Java Programming?
The File class is used to create objects that provide access to the files and directories of a local file system.
14. What is the difference between the paint() and repaint() methods in Java Programming?
The paint() method supports painting via a Graphics object. The repaint() method is used to cause paint() to be invoked by the AWT painting thread.
15. What is the difference between static and non-static variables in Java Programming?
A static variable is associated with the class as a whole rather than with specific instances of a class. Non-static variables take on unique values with each object instance.
16. What are the problems faced by Java programmers who don't use layout managers?
Without layout managers, Java programmers are faced with determining how their GUI will be displayed across multiple windowing systems and finding a common sizing and positioning that will work within the constraints imposed by each windowing system.
17. What advantage do Java's layout managers provide over traditional windowing systems?
Java uses layout managers to lay out components in a consistent manner across all windowing platforms. Since Java's layout managers aren't tied to absolute sizing and positioning, they are able to accommodate platform-specific differences among windowing systems.
18. How are the elements of a GridBagLayout organized in Java Programming?
The elements of a GridBagLayout are organized according to a grid. However, the elements are of different sizes and may occupy more than one row or column of the grid. In addition, the rows and columns may have different sizes.
19. How can a GUI component handle its own events in Java Programming?
A component can handle its own events by implementing the required event-listener interface and adding itself as its own event listener.
20. Which class should you use to obtain design information about an object in Java Programming?
The Class class is used to obtain information about an object's design.
21. Name primitive Java types?
The primitive types are byte, char, short, int, long, float, double, and boolean.
22. Does a class inherit the constructors of its superclass in Java Programming?
A class does not inherit constructors from any of its superclasses.
23. What is the Map interface in Java Programming?
The Map interface replaces the JDK 1.1 Dictionary class and is used associate keys with values.
A class that is declared without any access modifiers is said to have package or friendly access. This means that the class can only be accessed by other classes and interfaces that are defined within the same package.
25. What classes of exceptions may be caught by a catch clause in Java Programming?
A catch clause can catch any exception that may be assigned to the Throwable type. This includes the Error and Exception types.
The Reader/Writer class hierarchy is character-oriented, and the InputStream/OutputStream class hierarchy is byte-oriented.
27. What happens when a thread cannot acquire a lock on an object in Java Programming?
If a thread attempts to execute a synchronized method or synchronized statement and is unable to acquire an object's lock, it enters the waiting state until the lock becomes available.
28. What is the difference between the Font and FontMetrics classes in Java Programming?
The FontMetrics class is used to define implementation-specific properties, such as ascent and descent, of a Font object.
29. What are peerless components in Java Programming?
The peerless components are called light weight components.
30. Which package has light weight components in Java Programming?
javax.Swing package. All components in Swing, except JApplet, JDialog, JFrame and JWindow are lightweight components in Java Programming.
31. What do heavy weight components mean in Java Programming?
Heavy weight components like Abstract Window Toolkit (AWT), depend on the local windowing toolkit. For example, java.awt.Button is a heavy weight component, when it is running on the Java platform for Unix platform, it maps to a real Motif button. In this relationship, the Motif button is called the peer to the java.awt.Button. If you create two Buttons, two peers and hence two Motif Buttons are also created. The Java platform communicates with the Motif Buttons using the Java Native Interface. For each and every component added to the application, there is an additional overhead tied to the local windowing system, which is why these components are called heavyweight.
32. What is the difference between a Window and a Frame in Java Programming?
The Frame class extends Window to define a main application window that can have a menu bar.
33. When can an object reference be cast to an interface reference in Java Programming?
An object reference be cast to an interface reference when the object implements the referenced interface.
34. What is an object's lock and which object's have locks in Java Programming?
An object's lock is a mechanism that is used by multiple threads to obtain synchronized access to the object. A thread may execute a synchronized method of an object only after it has acquired the object's lock. All objects and classes have locks. A class's lock is acquired on the class's Class object.
35. What is the difference between a static and a non-static inner class in Java Programming?
A non-static inner class may have object instances that are associated with instances of the class's outer class. A static inner class does not have any object instances.
