Skip to main content

31 to 35 java questions

31. What is a Java Bean?
A Java Bean is a software component that has been designed to be reusable in a variety of different environments.

32. What are checked exceptions?
Checked exception are those which the Java compilerforces you to catch. e.g. IOException are checked Exceptions.

33. What are runtime exceptions?
Runtime exceptions are those exceptions that are thrown at runtime because of either wrong input data or because of wrong business logic etc. These are not checked by the compiler at compile time.

34. What is the difference between error and an exception?
An error is an irrecoverable condition occurring at runtime. Such as OutOfMemory error. These JVM errors and you can not repair them at runtime. While exceptions are conditions that occur because of bad input etc. e.g. FileNotFoundException will be thrown if the specified file does not exist. Or a NullPointerException will take place if you try using a null reference. In most of the cases it is possible to recover from an exception (probably by giving user a feedback for entering proper values etc.).

35. What is the purpose of finalization?
The purpose of finalization is to give an unreachable object the opportunity to perform any cleanup processing before the object is garbage collected. For example, closing a opened file, closing a opened database Connection.

Comments

Post a Comment

Popular posts from this blog

Panels in AWT

Panels: import java.applet.*; import java.awt.*; /*<applet code="PanelDemo" width=300 height=300></applet>*/ public class PanelDemo extends Applet { public void  init() { setLayout(new BorderLayout()); Panel pn=new Panel(); Button b1=new Button("Button 1"); pn.add(b1); Button b2=new Button("Button 2"); pn.add(b2); add(pn,"North"); Panel pe=new Panel(); Button b3=new Button("Button 3"); pe.add(b3); add(pe,"East"); Panel pw=new Panel(); Button b4=new Button("Button 4"); pw.add(b4); add(pw,"West"); Panel ps=new Panel(); Button b5=new Button("Button 5"); ps.add(b5); Button b6=new Button("Button 6"); ps.add(b6); add(ps,"South"); } }
Post a Comment
Read more

56 to 60 Java Questions

56. What is the purpose of apache tomcat? Apache server is a standalone server that is used to test servlets and create JSP pages. It is free and open source that is integrated in the Apache web server. It is fast, reliable server to configure the applications but it is hard to install. It is a servlet container that includes tools to configure and manage the server to run the applications. It can also be configured by editing XML configuration files. 57. Where pragma is used? Pragma is used inside the servlets in the header with a certain value. The value is of no-cache that tells that a servlets is acting as a proxy and it has to forward request. Pragma directives allow the compiler to use machine and operating system features while keeping the overall functionality with the Java language. These are different for different compilers. 58. Briefly explain daemon thread. Daemon thread is a low priority thread which runs in the background performs garbage collection operation for th...
Post a Comment
Read more

41 to 45 Java Questions

41. What is nested class? If all the methods of a inner class is static then it is a nested class. 42. What is HashMap and Map? Map is Interface and Hashmap is class that implements that. 43. What are different types of access modifiers? public: Any thing declared as public can be accessed from anywhere. private: Any thing declared as private can’t be seen outside of its class. protected: Any thing declared as protected can be accessed by classes in the same package and subclasses in the other packages. default modifier : Can be accessed only to classes in the same package. 44. What is the difference between Reader/Writer and InputStream/Output Stream? The Reader/Writer class is character-oriented and the InputStream/OutputStream class is byte-oriented. 45. What is servlet? Servlets are modules that extend request/response-oriented servers, such as java-enabled web servers. For example, a servlet might be responsible for taking data in an HTML order-entry form and applyi...
Post a Comment
Read more