Java Varibles

We would see following type of variables in Java:

• Local Variables
• Global variables

Local Variables : - A variable that is declared inside the method or block  is called local variable. Local variables within the method or block others methods or block can’t be used .There is no default values

public class localVariables

{

//local variables can be declared within the block

          static

          {

          float f;

System.out.println(f);                                             //CTE

                   f=10;

          System.out.println(f);

          }

// iib block

          {

                   double d;

                   System.out.println(d);                           //CTE

 //local variables can be declared within the method and should be instilized

                   d=10.5;

                   System.out.println(d);

          }

//local variables can be declared within the method

          void method1()

          {

                   int u;

                   System.out.println(u);

//local variables can be declared within the method and should be instilized

                   u=20;

                   System.out.println(u);

//local variables can't be out side

                   System.out.println(i);                 //CTE

                  

          }

// CONSTRUCTOR

          LocalVariables()

          {

                   int t;

                   System.out.println(t);                          //cte

                   t=56;

                   System.out.println(t);

          }

     public static void main(String[] args)

       {

           //object creation

           localVariables v1=new localVariables();

                     int i=10;

           System.out.println(i);                           //10

//local varibles should be instlized

           int j;

           System.out.println(j);                                   //CTE

 //local varibles should be used after the instilization only

           int k;

           int y=k;

           System.out.println(y);               // IILEGAL FORWARD REF

//local varibles any times of reinstilized

           i=20;

           System.out.println(i);

           i=50;

           System.out.println(i);

 //local variables can't be out side

                   system.out.println(u);                         // CTE

      

       }

}

Global variables :

Global variables contains default values its is based on the relevant data types

We can use any where in the class it’s based on type of global variables.

Class Variables :-

• Class variables are variables declared with in a class, outside any method, with the static keyword.
• Whenever the class loaded into the memory automatically loaded into static variables before main method

A class can have any number of methods to access the value of various kinds of methods

Default values for static variables  :

public class Defultvalues

{

          int i;

          String s1;

          double d;

          long l;

          float f;

          char c;

          boolean b;

          byte y;

          public static void main(String[] args)

          {

defultvalues v1=new defultvalues();

System.out.println(v1.i);            //0

System.out.println(v1.s1);          //null

System.out.println(v1.d);           //0.0

System.out.println(v1.l);            //0

System.out.println(v1.f);            //0.0

System.out.println(v1.c);           //single space

System.out.println(v1.b);  //false

System.out.println(v1.y);           //0

          }

}

Simple Program :

public class Staticv

{

// static varibles declaration

          static int i;

static

{

          static int h=50;                                             //cte

          System.out.println(i);                                    // cts

}        

          public static void main(String[] args)

          {

          // static varibles can't be used in side main method

          static double d=10;                                        //cte

          System.out.println(i);                                    // 0  

          }

}

Instance Variables (Non-static variables) : A variable that is declared inside the class but outside the method is called instance variable . It is not declared as static. public class Instancevariables { // non static varibles             int i=10;             double d=10;             int test1(int i)             {                      System.out.println(i);                                         return i;             }                       public static void main(String[] args)           {                    int j=10;                    Instancevariables ref=new Instancevariables();       // non static varbiles can be used when ever craeating object                    System.out.println(i);       // cte if cts i declared as static                    System.out.println(ref.i);                    System.out.println(ref.j);  //cte                    ref.i=20;                    //test1(ref.j); //non static members can be calling with ref of object                    ref.test1(10);                              } } Default values: In java default some value will be assigned  in the variables based on data type public class Defultvalues {           int i;           String s1;           double d;           long l;           float f;           char c;           boolean b;           byte y;           public static void main(String[] args)           { defultvalues v1=new defultvalues(); System.out.println(v1.i);            //0 System.out.println(v1.s1);          //null System.out.println(v1.d);           //0.0 System.out.println(v1.l);            //0 System.out.println(v1.f);            //0.0 System.out.println(v1.c);           //single space System.out.println(v1.b);  //false System.out.println(v1.y);           //0           } }

Default values

public class Defultvalues

{

          int i;

          String s1;

          double d;

          long l;

          float f;

          char c;

          boolean b;

          byte y;

          public static void main(String[] args)

          {

defultvalues v1=new defultvalues();

System.out.println(v1.i);            //0

System.out.println(v1.s1);          //null

System.out.println(v1.d);           //0.0

System.out.println(v1.l);            //0

System.out.println(v1.f);            //0.0

System.out.println(v1.c);           //single space

System.out.println(v1.b);  //false

System.out.println(v1.y);           //0

          }

}