Saturday, 28 April 2012

JAVA interview questions 22

Q211. What method must be implemented by all threads? 
All tasks must implement the run() method, whether they are a subclass of Thread or implement the Runnable interface. 

Q212. What methods are used to get and set the text label displayed by a Button object? 
getLabel() and setLabel() 

Q213. Which Component subclass is used for drawing andpainting? 

Q214. What are synchronized methods and synchronized statements? 
Synchronized methods are methods that are used to control access to an object. A thread only executes a synchronized method after it has acquired the lock for the method's object or class. Synchronized statements are similar to synchronized methods. A synchronized statement can only be executed after a thread has acquired the lock for the object or class referenced in the synchronized statement. 

Q215. What are the two basic ways in which classes thatcan be run as threads may be defined? 
A thread class may be declared as a subclass of Thread, or it may implement the Runnable interface. 

Q216. 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. 

Q217. What is the difference between an if statement and aswitch statement? 
The if statement is used to select among two alternatives. It uses a boolean expression to decide 
which alternative should be executed. The switch statement is used to select among multiple 
alternatives. It uses an int expression to determine which alternative should be executed. 

Q218. What happens when you add a double value to a String? 
The result is a String object. 

Q219. What is the List interface? 
The List interface provides support for ordered collections of objects 

Q220.What is an Exception? 
Ans.An unwanted, unexpected event that disturbs normal flow of the program is called Exception.Example: FileNotFondException. 

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