Session On Java Basics
i) Is java purely object oriented language ?
JAVA is not because it supports Primitive datatype such as int, byte, long… etc, to be used, which are not objects.
ii) Write once run anywhere concept ?
Java source code is compiled into class file . This file is executed on any platform which has JVM
iii) public static void main(String args)
java environment needs acces to execute it –> public
without creating instance need to run main method –> static
main method doesnt return anything — > void
all arguments passed are of string type and placed in a string array –> args
iv) diff between == and .equals()
== compare reference
.equals compares the content
v) Access specifier a quick play
public , private protected , default
vi) final , finally and finalize
final – to declare constants and avoid inheriting a class
finally – in exception handling to run a piece of code even exception occurs or not
finalize – whenever garbage collection is about to occur finalize method will be called
vii) java API swing , applets , servlets
viii) no global variable in java ?
ix) Numeric promotion
after any arithmetic operation (byte,char,short)–>int–> long–>double
x) first argument of args in C and java
in C first argument will be the name of the program but in java it is the first argument passed
xi) library methods stringtokenizer
StringTokenizer st=new StringTokenizer(“karthik:be:cse”,”:”,false);
points about java :
* No pointers - Unauthorized access prevention
* No operator overloading - ambiguity is possible
* No destructor – instead finally is present
* Multithreading made thro language – concurency
* new to allocate memory to object … memory release done by garbage collector