Java Interview Questions - Page 6
Question: What is the Vector class?
Answer: The Vector class provides the capability to
implement a growable array of objects What modifiers may be used with an
inner class that is a member of an outer class? A (non-local) inner class
may be declared as public, protected, private, static, final, or abstract.
Question: If a method is declared as protected, where may the method be
accessed?
Answer: 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.
Question: What is an Iterator interface?
Answer: The Iterator interface is used to step
through the elements of a Collection.
Question: How many bits are used to represent Unicode, ASCII, UTF-16, and UTF-8
characters?
Answer: 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.
Question: What is the difference between yielding and sleeping?
Answer: 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.
Question: Is sizeof a keyword?
Answer: The sizeof operator is not a keyword.
Question: What are wrapped classes?
Answer: Wrapped classes are classes that allow
primitive types to be accessed as objects.
Question: Does garbage collection guarantee that a program will not run out of
memory?
Answer: No, it doesn't. 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
Question: What is the difference between preemptive scheduling and time
slicing?
Answer: 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.
Question: Name Component subclasses that support painting.
Answer: The Canvas, Frame,
Panel, and Applet classes support painting.
Question: What is a native method?
Answer: A native method is a method that is
implemented in a language other than Java.