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Arrary in java with example

Array: - 

An array represents a group of elements of same data type. .

                                                         OR

              An array is collection of elements with same data type.

They are two type :

1) Single dimensional array.

 2) Two dimensional arrays  OR  (multi dimensional array).

1) Single dimensional arrays : - 

A Single dimensional array represents is a single row or a single column of an elements.

Syntax:-   

       Datatype arrayvariablename[]=new datatype[size];

       Int a[]=new int[5];

                                        OR

     Datatype arrayname[]={var1,var2,….,varn};

     Int a[]={2,4,…,n};

Single dimensional array stores values:-

2) Two dimensional arrays : - 

A Two dimensional array represents is a several rows and columns of an elements.

Syntax:-   

       Datatype arrayvariablename[][]=new datatype[row size][column size];

       Int a[][]=new int[5][5];

                                        OR

     Datatype arrayname[][]={{var1,var2,….,varn},{var1,var2,….,varn},…..,{ var1,var2,….,varn }};

     Int a[]={{11,12,13,14,15},{21,22,23,24,25},{31,32,33,3,4,35}};

Two dimensional array stores values:-

Example Program:-

public class Array_Example {

              public static void main(String args[]){

             int[] a=new int[5];

                  for(int i=0;i<5;i++){

                      a[i]=i+1;

                      System.out.println(""+a[i]);

                  }

          }

   }

Java Keywords

A Keyword is that which have a special meaning. Keywords is a word that we can identify easily in java program, it shows keywords in blue color. Keywords start with small letter.

List of keywords:-

abstract         assert

boolean          break             byte

case                catch              char              class            const       continue

default           do                   double   

else                 enum             extends

final               finally            float for

goto    

if                    implements    import         instanceof    int          interface

long  

native             new

package         private            protected     public

return    

short            static                 strictfp         super           switch    synchronized 

this              throw                 throws         transient      try  

void             volatile

while

Exceptions in JAVA

Exceptions:-

An exception is a problem that arises during the execution of a program. An exception can occur for many different reasons.

Exceptions divided into 3 categories:-

1.        Checked Exceptions (Compile time Exception):-

These are Exceptions occurs when the program has wrong syntax or the grammar of the language. These exceptions can be identifying during compilation time. Compiler identifies the checked exceptions. Desk checking mechanism is the solution of compile time errors (checked exceptions).

2.       Unchecked Exception (Runtime Exceptions):-

These Exceptions are detected by JVM at the time of running the program. “Exception handling” mechanism is solving these types of exceptions.

3.       Errors:-

These errors represent bad logic. These errors are not detected by the compiler or JVM. Logical errors are detected by comparing the program output with manually calculated result.

Ø  An exception is an error that can be handled. When there is an exception JVM displays exception name & its description.

Ø  An error cannot be handled.

Exception Handling Mechanism:-

1.       Try block.

2.       Catch block.

3.       Finally block.

4.       Throws.

5.       Throw.

If we have exception doubt in the program that can implement in try block.

If exception is available it will throws corresponding catch block.

There is an exception catch and finally block is executed.

An exception is not available catch will not execute and finally block is execute.

Finally block has closing connection.

We can use more than one catch block.

Example:-

try{

Statement; // implement code

}

catch(Exception exobj)   //exobj is object of an exception,  it has exception details.

{

out.println(exobj);  //it display exception details

}

catch(Exception ex)

        {

            out.println(ex);  //it display exception details

        }

finally {           

            out.close();   //close connection

        }

Example Program:-

public class Exceptionss {

    public static void main(String a[]){

        int d=5,b=10,c;

        try{

            c=d/b;

            if(d<10)

            {

                MyException me=new MyException("error");

                throw me;

            }

        }

    catch(ArithmeticException ae)

    {

        ae.printStackTrace();

    }

    catch(MyException me)

    {

        System.out.println(me);

    }

    }

}

class MyException extends Exception

{

    String msg;

    MyException()

    {

    }

MyException(String msg)

{

    super(msg);

    this.msg=msg;

  }

}