Wednesday, 25 April 2012

JAVA interview questions 10

Q91. How are commas used in the intialization and iterationparts of a for statement? 
Commas are used to separate multiple statements within the initialization and iteration parts of a for statement. 

Q92. What is the purpose of the wait (), notify (), andnotifyAll() methods? 
The wait(),notify(), and notifyAll() methods are used to provide an efficient way for threads to wait for a shared resource. When a thread executes an object's wait() method, it enters the 
waiting state. It only enters the ready state after another thread invokes the object's notify() or notifyAll() methods.. 

Q93. What is an abstract method? 
An abstract method is a method whose implementation is deferred to a subclass. 

Q94. How are Java source code files named? 
A Java source code file takes the name of a public class or interface that is defined within the 
file. A source code file may contain at most one public class or interface. If a public class or 
interface is defined within a source code file, then the source code file must take the name of the public class or interface. If no public class or interface is defined within a source code file, then 
the file must take on a name that is different than its classes and interfaces. Source code files use the .java extension. 

Q95. What is the relationship between the Canvas class andthe Graphics class? 
A Canvas object provides access to a Graphics object via its paint() method. 

Q96. What are the high-level thread states? 
The high-level thread states are ready, running, waiting, and dead. 

Q97. What value does read() return when it has reached theend of a file? 
The read() method returns -1 when it has reached the end of a file. 

Q98. Can a Byte object be cast to a double value? 
No, an object cannot be cast to a primitive value. 

Q99. What is the difference between a static and a nonstaticinner class? 
A non-static inner class may have object instances that are associated with instances of the class's outer class. A static inner class does not have any object instances. 

Q100. What is the difference between the String andStringBuffer classes? 
String objects are constants. StringBuffer objects are not.

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