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Java Interview Questions and Answers
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.
What is the immediate superclass of the Applet class?
Panel
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.
Name three Component subclasses that support painting.
The Canvas, Frame, Panel, and Applet classes support painting.
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. What is the immediate superclass of the Dialog class?
Window.What is clipping?
Clipping is the process of confining paint operations to a limited area
or shape.
What is a native method?
A native method is a method that is implemented in a language other than
Java.
Can a for statement loop indefinitely?
Yes, a for statement can loop indefinitely. For example, consider the
following: for(;;) ;
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
When a thread blocks on I/O, what state does it enter?
A thread enters the waiting state when it blocks on I/O.
To what value is a variable of the String type automatically
initialized?
The default value of a String type is null.
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.
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.
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.
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.
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.
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.
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