What restrictions are placed on the location of a package statement within a source code file?

A package statement must appear as the first line in a source code file (excluding blank lines and comments).

What is the immediate superclass of the Dialog class?

Window.

What is the difference between set and list?

Set stores elements in an unordered way but does not contain duplicate elements, whereas list stores elements in an ordered way but may contain duplicate elements.

What’s the use of JAVAP tool ?

javap disassembles compiled Java files and spits out representation of the Java program. This is a useful option when the original source code is not available.

What modifiers may be used with top-level class?-

public, abstract and final can be used for top-level class.

To what value is a variable of the String type automatically initialized

The default value of an String type is null.

What an I/O filter

An I/O filter is an object that reads from one stream and writes to another, usually altering the data in some way as it is passed from one stream to another.

What is a StringBuffer class and how does it differs from String class?

StringBuffer is a peer class of String that provides almost all functionality of strings. String represents fixed-length, immutable character sequences. Comparatively StringBuffer represents mutable, growable and writeable character sequences. But StringBuffer does not create new instances as string so it’s more efficient when it comes to intensive concatenation operation.

What is the difference between Integer and int?-

a) Integer is a class defined in the java. lang package, whereas int is a primitive data type defined in the Java language itself. Java does not automatically convert from one to the other. b) Integer can be used as an argument for a method that requires an object, whereas int can be used for calculations.

What is the difference between doPost and doGet methods

?– a) doGet() method is used to get information, while doPost() method is used for posting information. b) doGet() requests can’t send large amount of information and is limited to 240-255 characters. However, doPost()requests passes all of its data, of unlimited length. c) A doGet() request is appended to the request URL in a query string and this allows the exchange is visible to the client, whereas a doPost() request passes directly over the socket connection as part of its HTTP request body and the exchange are invisible to the client.