Java
In this tutorial we will learn about final variables in Java programming language.
final
If the final keyword is added to a variable then it becomes a constant and its value can't be modified later.
final type varName = val;
Where, varName is the name of the variable and its data type is represented by type.
varName
type
We are assigning a value to the variable represented by val.
val
And this is a constant as we are using the final keyword.
In the following example we are creating an interger variable MULTIPLY and declaring it final. We are assigning integer value 100 to it.
MULTIPLY
Since, we are declaring it as final so, any attempt to modify its value will give error.
class Example { public static void main(String[] args) { // creating a final variable final int MULTIPLY = 100; // output System.out.println("Value of the MULTIPLY constant: " + MULTIPLY); // the following code will return error // MULTIPLY = 1; } }
Output:
Value of the MULTIPLY constant: 100
If we uncomment the line MULTIPLY = 1; and re-run our code. We will get the following error.
MULTIPLY = 1;
Main.java:11: error: cannot assign a value to final variable MULTIPLY MULTIPLY = 1; ^ 1 error
In the following example we are creating multiple constants.
class Example { public static void main(String[] args) { // creating a final variables final char CH = 'a'; final byte B = 0; final short S = 1; final int I = 10; final long L = 100; final float F = 123.45F; final double D = 123.456; final String STR = "Hello World"; // output System.out.println("Value of the CH constant: " + CH); System.out.println("Value of the B constant: " + B); System.out.println("Value of the S constant: " + S); System.out.println("Value of the I constant: " + I); System.out.println("Value of the L constant: " + L); System.out.println("Value of the F constant: " + F); System.out.println("Value of the D constant: " + D); System.out.println("Value of the STR constant: " + STR); } }
$ javac Example.java $ java Example Value of the CH constant: a Value of the B constant: 0 Value of the S constant: 1 Value of the I constant: 10 Value of the L constant: 100 Value of the F constant: 123.45 Value of the D constant: 123.456 Value of the STR constant: Hello World