What are Java Access Specifiers? Or What is the difference between public, private, protected and default Access Specifiers? Or What are different types of access modifiers?

Access specifiers are keywords that determine the type of access to the member of a class. These keywords are for allowing
privileges to parts of a program such as functions and variables. These are:
• Public : accessible to all classes
• Protected : accessible to the classes within the same package and any subclasses.
• Private : accessible only to the class to which they belong
• Default : accessible to the class to which they belong and to subclasses within the same package

What is the difference between a while statement and a do statement?

A while statement (pre test) checks at the beginning of a loop to see whether the next loop iteration should occur. A do while statement (post test) checks at the end of a loop to see whether the next iteration of a loop should occur. The do statement will always execute the loop body at least once.

What is the GregorianCalendar class?

The GregorianCalendar provides support for traditional Western calendars.

What is the Java API?

The Java API is a large collection of ready-made software components that provide many useful capabilities, such as graphical user interface (GUI) widgets.

What is the difference between final, finally and finalize? What do you understand by the java final keyword? Or What is final, finalize() and finally? Or What is finalize() method? Or What is the difference between final, finally and finalize? Or What does it mean that a class or member is final? o final - declare constant o finally - handles exception o finalize - helps in garbage collection

Variables defined in an interface are implicitly final. A final class can’t be extended i.e., final class may not be subclassed. This is done for security reasons with basic classes like String and Integer. It also allows the compiler to make some optimizations, and makes thread safety a little easier to achieve. A final method can’t be overridden when its class is inherited. You can’t change value of a final variable (is a constant). finalize() method is used just before an object is destroyed and garbage collected. finally, a key word used in exception handling and will be executed whether or not an exception is thrown. For example, closing of open connections is done in the finally method.

Why oracle Type 4 driver is named as oracle thin driver?

Oracle provides a Type 4 JDBC driver, referred to as the Oracle “thin” driver. This driver includes its own implementation of a TCP/IP version of Oracle’s Net8 written entirely in Java, so it is platform independent, can be downloaded to a browser at runtime, and does not require any Oracle software on the client side. This driver requires a TCP/IP listener on the server side, and the client connection string uses the TCP/IP port address, not the TNSNAMES entry for the database name.

What if the static modifier is removed from the signature of the main method? Or What if I do not provide the String array as the argument to the method?

Program compiles. But at runtime throws an error “NoSuchMethodError”.

What are the differences between == and .equals() ? Or what is difference between == and equals Or Difference between == and equals method Or What would you use to compare two String variables - the operator == or the method equals()? Or How is it possible for two String objects with identical values not to be equal under the == operator?

The == operator compares two objects to determine if they are the same object in memory i.e. present in the same memory location. It is possible for two String objects to have the same value, but located in different areas of memory.
== compares references while .equals compares contents. The method public boolean equals(Object obj) is provided by the Object class and can be overridden. The default implementation returns true only if the object is compared with itself, which is equivalent to the equality operator == being used to compare aliases to the object. String, BitSet, Date, and File override the equals() method. For two String objects, value equality means that they contain the same character sequence. For the Wrapper classes, value equality means that the primitive values are equal.

public class EqualsTest { public static void main(String[] args) { String s1 = “abc”; String s2 = s1; String s5 = “abc”; String s3 = new String(”abc”); String s4 = new String(”abc”); System.out.println(”== comparison : ” + (s1 == s5)); System.out.println(”== comparison : ” + (s1 == s2)); System.out.println(”Using equals method : ” + s1.equals(s2)); System.out.println(”== comparison : ” + s3 == s4); System.out.println(”Using equals method : ” + s3.equals(s4)); } }

Output
== comparison : true
== comparison : true
Using equals method : true
false
Using equals method : true

Expain the reason for each keyword of public static void main(String args[])?

public- main(..) is the first method called by java environment when a program is executed so it has to accessible from java environment. Hence the access specifier has to be public.
static: Java environment should be able to call this method without creating an instance of the class , so this method must be declared as static.
void: main does not return anything so the return type must be void
The argument String indicates the argument type which is given at the command line and arg is an array for string given during command line.

What is Byte Code? Or What gives java it’s “write once and run anywhere” nature?

All Java programs are compiled into class files that contain bytecodes. These byte codes can be run in any platform and hence java is said to be platform independent.

If you’re overriding the method equals() of an object, which other method you might also consider?

hashCode()

What is meant by pass by reference and pass by value in Java?

Pass by reference means, passing the address itself rather than passing the value. Pass by value means passing a copy of the value.

Java How to Program

Harvey M. Deitel, ...

Basic JavaScript Examples

Write text with JavaScript
Write HTML tags with JavaScript
JavaScript in the body section
JavaScript in the head section
An external JavaScript
Examples explained

Whom this page is for

In its present form, this page is for the absolute beginner to Javascript. Some knowledge of HTML is assumed. For more information on HTML, check out my Links Page. Further on, familiarity with C++ will also be useful since these two are somewhat similar in syntax and also because Javascript is Object Oriented.
The Tips page contain some very simple but useful Javascript samples along with explanations. You can use them without knowing much about Javascript. On the Examples page, the code is somewhat longer(around 15 to 25 lines each). This page is still under construction but most of the things work. On the Links page, you will find links to lots of Javascript related resources on the web and if that's not enough, you can buy a couple of Javascript books from the BookStore. I would recommend Javascript Bible by Danny Goodman.

Who is the beginner?

No, it's not you. It's me. By the title, all I meant was that this is my Guide to Javascript. I have just started studying Javascript and this is my way of doing it. Just thought I'd warn you...
As I learn Javascript, I'll be constantly improving this web site. So if you don't find anything of interest here now, please do come back later.

What is JavaScript?

JavaScript can be thought of as an extension to HTML which allows authors to incorporate some functionality in their web pages. So now, whenever the user presses the SUBMIT button, you don't necessarily have to invoke a cgi script to do the processing. If it is something simple, you can do the processing locally using Javascript and give back the results. JavaScript can also be used in a number of ways to spice up your page.