What is
blank final variable in Java
Blank final variable in Java is a final variable which is not initialized
while declaration, instead they are initialized on constructor. Java compiler
will complain if blank final variable
is not initialized during construction. If you have more than one constructor
or overloaded
constructor in your class then blank
final variable must be initialized in all of them, failing to do so is a compile
time error in Java. Alternatively you can use constructor chaining to call
one constructor from other using this keyword, in order to delegate initialization of blank final variable in
Java. In this Java tutorial we will see What is blank final variable in
Java and a code example on How to use blank final variable.
How to use blank final variable in Java with Example
Blank final variable is like any other final variable but must be initialized
in constructor
as shown in below example. If you don't initialize or forget to initialize blank final variable then compiler will complain about it by throwing compile time error. static and final variable are treated as compile time constant and there value is replaced during compile time only.
/**
*
* Java program to demonstrate that blank final variable in Java
*
* Java program to demonstrate that blank final variable in Java
* must be initialized in
constructor.
* Failing to initialized blank final variable will result in compile time error.
* @author http://java67.blogspot.com
*/
public class BlankFinalVariable {
private final int blankFinalVariable; //must be initialized in constructor
public BlankFinalVariable(){
this(6); // this is Ok
//this.blankFinalVariable = 3;
}
public BlankFinalVariable(int number){
this.blankFinalVariable = number;
}
public static void main(String args[]) {
BlankFinalVariable clazz = new BlankFinalVariable();
System.err.println("Value of blank final variable in Java : " + clazz.blankFinalVariable);
}
}
Output:
Value of blank final variable in Java : 6
Output:
Value of blank final variable in Java : 6
* Failing to initialized blank final variable will result in compile time error.
* @author http://java67.blogspot.com
*/
public class BlankFinalVariable {
private final int blankFinalVariable; //must be initialized in constructor
public BlankFinalVariable(){
this(6); // this is Ok
//this.blankFinalVariable = 3;
}
public BlankFinalVariable(int number){
this.blankFinalVariable = number;
}
public static void main(String args[]) {
BlankFinalVariable clazz = new BlankFinalVariable();
System.err.println("Value of blank final variable in Java : " + clazz.blankFinalVariable);
}
}
Output:
Value of blank final variable in Java : 6
Output:
Value of blank final variable in Java : 6
That's all on What is blank final variable in Java and how to use
them. If you wan to learn more about What
is final variable or final class in Java, then see that link. Another
important point to note is that you can not override final method and can not
sub class final class, those will result in compile time error.
Other Java fundamental tutorial you may like
When do some one should use blank final variable? Do you have a genuine use case for blank final variables in Java ?
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