Default values to instance variable:
Instance variable: the variables which are defined inside the
class and outside of the method
Datatype default values to
instance variable
------------------------------------------------
byte --> 0
short --> 0
int -->
0
long --> 0
float --> 0.0
double --> 0.0
char --> space
boolean -->
false ***
String --> null
class ref var --> null
inte;rface ref variable -->
null
ex1
package OOPSBasics;
public class Student
{
//
Instance variable (or) global var
//
Declare int, long, float,double, char, boolean , String var
int
i;
long
l;
float
f;
double
d;
char
ch ;
boolean
b;
String
s;
public
static void main(String[] args) {
// create obj for student class
// syntax:
classname objref= new className();
int
a =10; // local variable
//
create obj for student class with ref variable s1
Student
s1 = new Student();
//
Default value of instance variables i
System.out.println("
Default value of instance variables i -->" + s1.i);
//Default
value of instance variables long
System.out.println("
Default value of instance variables long -->" + s1.l);
//Default
value of instance variables float
System.out.println("
Default value of instance variables float -->" + s1.f);
//Default
value of instance variables double
System.out.println("
Default value of instance variables double-->" + s1.d);
//Default
value of instance variables char
System.out.println("
Default value of instance variables char-->" + s1.ch);
//Default
value of instance variables boolean
System.out.println("
Default value of instance variables boolean -->" + s1.b);
//Default
value of instance variables String
System.out.println("
Default value of instance variables String-->" + s1.s);
//
store i= 10
s1.i
= 10;
// 0
-> 10
//
store l= 29097
s1.l
= 29097;
//
0 --> 2907
//
Store f=2.3f;
s1.f
= 2.3f;
// 0.0 --> 2.3
//
Store d= 3.455;
s1.d = 3.455d;
//
0.0 --> 3.455
//
Store gender = 'M';
s1.ch
= 'M';
//
space --> 'M'
//
Store .b= true;
s1.b =
true;
// false --> true
//
Store name = "Ram";
s1.s = "Ram";
// null -->
Ram
//
display
//
Default value of instance variables i
System.out.println("
Default value of instance variables i -->" + s1.i);
//Default
value of instance variables long
System.out.println("
Default value of instance variables long -->" + s1.l);
//Default
value of instance variables float
System.out.println("
Default value of instance variables float -->" + s1.f);
//Default
value of instance variables double
System.out.println("
Default value of instance variables double-->" + s1.d);
//Default
value of instance variables char
System.out.println("
Default value of instance variables char-->" + s1.ch);
//Default
value of instance variables boolean
System.out.println("
Default value of instance variables boolean -->" + s1.b);
//Default
value of instance variables String
System.out.println("
Default value of instance variables String-->" + s1.s);
}
}
o/p:
Default value of instance variables i -->0
Default value of instance variables long
-->0
Default value of instance variables float
-->0.0
Default value of instance variables
double-->0.0
Default value of instance variables char-->
Note :
·
Default values are available only for instance
variables, but not for local variables.
·
Only instance variables have default values.
·
Who
assigns default values to instance variables.
·
The compiler assigns these default values based
on the data type of the instance variable.
Ex : Local var has no default
values.
package ClassBAsics;
public class Student
{
int
i; // 0
long
l;// 0
float
f;
double
d;
char
gender;
boolean
b;
String
name; // Instance variables
String
Address;
public static void add()
{
// local variables a,b , res
}
public
static void main(String[] args) {
Student
s1 = new Student();
////
s1.i =10 ;
System.out.println("s1.i="+
s1.i);// 0
s1.i
=10 ;
System.out.println("s1.i="+
s1.i);// 10
System.out.println("s1.l="+
s1.l);
System.out.println("s1.float
="+ s1.f);
System.out.println("s1.
doube="+ s1.d);
System.out.println("s1.char="+
s1.gender);
System.out.println("s1.boolean="+
s1.b);
System.out.println("s1.string
="+ s1.name);
//
Declare local variable i.e a
//
local variable : There is no default
value = 0 for local variable
//
display a var
//CE: the local variable 'a' may not have been
initialized
// all local variables must be initilaised with
some value
//
store a =25
//
display a
}
}
No comments:
Post a Comment