Short Technical Notes

  What is Constructor in Java? A constructor is a member method Should have same name as class name It will never return anything It will use to allocate memory.  class ConstructorExample { int x ; String y ; public ConstructorExample() { //constructor can be used to initialize default values for variables x = 5; y = "Hello World" ; } //parameterize Constructor public ConstructorExample( int k , String str ) { //constructor can be used to initialize default values for variables x = k ; y = str ; } } class inside a class(Inner Class) class Outer { int i ; class Inner { public void show() { System. out .println( "Method inside inner class" ); } } static class InnerStatic { public void show() { System. out .println( "Method inside static inner class" ); ...

Linklist Representation  Node.java   public class Node { int data ; Node next ; Node( int data , Node next ){ this . data = data ; this . next = next ; } } LinkList.java public class LinkList { Node head ; public void insert( int data ) { Node node = new Node( data , null ); if ( head == null ) { head = node ; } else { Node currentNode = head ; while ( currentNode . next != null ) { currentNode = currentNode . next ; } currentNode . next = node ; } } public void inserAtStart( int data ) { Node node = new Node( data , null ); node . next = head ; head = node ; } public void insertAt( int index , int data ) { Node node = new Node( data , null ); // if index is 0 or head is null then insert at start if ( index == 0 || head == null ) { inserAtStart( data ); ...

public class NumberPattern { public static void main(String a []) { for ( int i = 1; i <=4; i ++) { for ( int j =0; j <4; j ++) { int sum = i + j ; // if sum is greater than 4 then subtract 4 from the sum otherwise print the sum System. out .print( sum > 4 ? sum - 4+ " " : sum + " " ); } System. out .println(); } } }

This can be done in a very simple way. "printf" returns PrintStream. So we can put it in if block and no need to use semicolon. public class HelloClass { public static void main(String a []) { if (System. out .printf( "Hello World" ) == null ) { //No need to define something here } } } //OUTPUT:   // Hello World

Datatypes in Java int 4 bytes short int 2 bytes long int 8 bytes byte 1 byte float  4 bytes double 8 bytes char 2 bytes Character to ASCII conversion in JAVA          class CharToASCII { public static void main(String a []) { char c1 = 'A' ; char c2 = 'a' ; System. out .print(( int ) c1 ); // OUTPUT: 65 System. out .print(( int ) c2 ); // OUTPUT: 97 System. out .print(( char )66); // OUTPUT: B  --> ASCII to i nt conversion           }        } "printf" is also available in JAVA            class  PrintfInJava {              public   static   void  main(String  a []) { int   i  =  4 ; int   j  =  7 ;   ...