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Java Interview Questions
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Java, the language, is a high-level object-oriented programming language, influenced in various ways by C, C++, and Smalltalk, with ideas borrowed from other languages as well (see O'Reilly's History of Programming Languages). Its syntax was designed to be familiar to those familiar with C-descended "curly brace" languages, but with arguably stronger OO principles than those found in C++, static typing of objects, and a fairly rigid system of exceptions that require every method in the call stack to either handle exceptions or declare their ability to throw them. Garbage collection is assumed, sparing the developer from having to free memory used by obsolete objects.
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Java FAQs - 1 |
Java FAQs - 2 |
Java FAQs - 3 |
Java FAQs - 4 |
Java FAQs - 5
Java FAQs - 6 |
Java FAQs - 7 |
Java FAQs - 8 |
Java FAQs - 9 |
Java FAQs - 10
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Core Java Interview Questions - Part4
26. What are wrapped classes?
Wrapped classes are classes that allow primitive types to be accessed as
objects.
27. Does garbage collection guarantee that a program will not run out of memory?
Garbage collection does not guarantee that a program will not run out of memory.
It is
possible for programs to use up memory resources faster than they are garbage
collected.
It is also possible for programs to create objects that are not subject to
garbage collection
28. What restrictions are placed on the location of a package statement
within a source code file?
A package statement must appear as the first line in a source code file
(excluding blank
lines and comments).
29. Can an object's finalize() method be invoked while it is reachable?
An object's finalize() method cannot be invoked by the garbage collector while
the object
is still reachable. However, an object's finalize() method may be invoked by
other
objects.
30. What is the immediate superclass of the Applet class?
Panel
31. What is the difference between preemptive scheduling and time slicing?
Under preemptive scheduling, the highest priority task executes until it enters
the waiting
or dead states or a higher priority task comes into existence. Under time
slicing, a task
executes for a predefined slice of time and then reenters the pool of ready
tasks. The
scheduler then determines which task should execute next, based on priority and
other factors.
32. Name three Component subclasses that support painting.
The Canvas, Frame, Panel, and Applet classes support painting.
33. What value does readLine() return when it has reached the end of a file?
The readLine() method returns null when it has reached the end of a file.
34. What is the immediate superclass of the Dialog class?
Window
35. What is clipping?
Clipping is the process of confining paint operations to a limited area or
shape.
36. What is a native method?
A native method is a method that is implemented in a language other than Java.
37. Can a for statement loop indefinitely?
Yes, a for statement can loop indefinitely. For example, consider the following:
for(;;) ;
38. What are order of precedence and associativity, and how are they used?
Order of precedence determines the order in which operators are evaluated in
expressions. Associatity determines whether an expression is evaluated
left-to-right or
right-to-left
39. When a thread blocks on I/O, what state does it enter?
A thread enters the waiting state when it blocks on I/O.
40. To what value is a variable of the String type automatically initialized?
The default value of an String type is null.
41. What is the catch or declare rule for method declarations?
If a checked exception may be thrown within the body of a method, the method
must
either catch the exception or declare it in its throws clause.
42. What is the difference between a MenuItem and a CheckboxMenuItem?
The CheckboxMenuItem class extends the MenuItem class to support a menu item
that
may be checked or unchecked.
43. What is a task's priority and how is it used in scheduling?
A task's priority is an integer value that identifies the relative order in
which it should be
executed with respect to other tasks. The scheduler attempts to schedule higher
priority
tasks before lower priority tasks.
44. What class is the top of the AWT event hierarchy?
The java.awt.AWTEvent class is the highest-level class in the AWT event-class
hierarchy.
45. When a thread is created and started, what is its initial state?
A thread is in the ready state after it has been created and started.
46. Can an anonymous class be declared as implementing an interface and
extending a
class?
An anonymous class may implement an interface or extend a superclass, but may
not be
declared to do both.
47. What is the range of the short type?
The range of the short type is -(2^15) to 2^15 - 1.
48. What is the range of the char type?
The range of the char type is 0 to 2^16 - 1.
49. In which package are most of the AWT events that support the
event-delegation
model defined?
Most of the AWT-related events of the event-delegation model are defined in the
java.awt.event package. The AWTEvent class is defined in the java.awt package.
50. What is the immediate superclass of Menu?
MenuItem
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