Java Interview Questions and Answers
Question - 51 : - How many bits are used to represent Unicode, ASCII, UTF-16, and UTF-8 characters?
Answer - 51 : - 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 - 52 : - What's the main difference between a Vector and an ArrayList?
Answer - 52 : - Java Vector class is internally synchronized and ArrayList is not.
Question - 53 : - What are wrapped classes?
Answer - 53 : - Wrapped classes are classes that allow primitive types to be accessed as objects.
Question - 54 : - Does garbage collection guarantee that a program will not run out of memory?
Answer - 54 : - 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 - 55 : - What is the difference between preemptive scheduling and time slicing?
Answer - 55 : - 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 - 56 : - What is the purpose of the System class?
Answer - 56 : - The purpose of the System class is to provide access to system resources.
Question - 57 : - What is the purpose of the finally clause of a try-catch-finally statement?
Answer - 57 : - The finally clause is used to provide the capability to execute code no matter whether or not an exception is thrown or caught.
Question - 58 : - What is the Locale class?
Answer - 58 : - The Locale class is used to tailor program output to the conventions of a particular geographic, political, or cultural region.
Question - 59 : - What is an abstract method?
Answer - 59 : - An abstract method is a method whose implementation is deferred to a subclass. Or, a method that has no implementation.
Question - 60 : - What is the difference between interface and abstract class?
Answer - 60 : - interface contains methods that must be abstract; abstract class may contain concrete methods. interface contains variables that must be static and final; abstract class may contain non-final and final variables. members in an interface are public by default, abstract class may contain non-public members. interface is used to "implements"; whereas abstract class is used to "extends". interface can be used to achieve multiple inheritance; abstract class can be used as a single inheritance. interface can "extends" another interface, abstract class can "extends" another class and "implements" multiple interfaces. interface is absolutely abstract; abstract class can be invoked if a main() exists. interface is more flexible than abstract class because one class can only "extends" one super class, but "implements" multiple interfaces. If given a choice, use interface instead of abstract class.