Constants
in Java
Sometimes we may need
to define some values as constants in our program. Nobody should be able
to change these values and it should be constant every time. One example for a
constant is the mathematical constant “pi” which has the value 3.14 every time.
To define a variable
as constant, we just need to add the keyword “final” in front of the variable
declaration.
Example
1
final int distance =
30;
The above statement
declares the int variable “distance” as a constant with a value 30.
We cannot change the value of distance at any point of time in the program.
Later if we try to do that by using statements like “distance=40;”, Java will
throw errors at compile time itself.
It is not mandatory
that you need to assign values of constants during initialization itself.
Example
2
final int distance;
distance = 30;
distance = 30;
Here we are first
defining the int variable distance as a constant. Later we are assigning the
value 30 to our constant. Once this value is assigned, we cannot change this
value in the program and if we try to do that by using statements like
“distance=40;”, Java will throw errors at compile time itself.
Various Constant
Types
Primitive Data Types
|
byte
|
short
|
int
|
long
|
float
|
double
|
boolean
|
char
|
You can define any of
these type variables as constants by just adding the keyword “final” when we
declare the variable.
Eg1: final int distance = 30;
Eg2: final float pi = 3.14f;
Eg2: final float pi = 3.14f;
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