A final variable which is left without initialization is known as blank final variable.
Generally, we initialize instance variables in the constructor. If we miss out they will be initialized by the constructors by default values. But, the final blank variables will not be initialized with default values. So if you try to use a blank final variable without initializing in the constructor, a compile time error will be generated.
Example
public class Student {
public final String name;
public void display() {
System.out.println("Name of the Student: "+this.name);
}
public static void main(String args[]) {
new Student().display();
}
}Compile time error
On compiling, this program generates the following error.
Student.java:3: error: variable name not initialized in the default constructor private final String name; ^ 1 error
Therefore, it is mandatory to initialize final variables once you declare them. If more than one constructor is provided in the class, you need to initialize the blank final variable in all the constructors.
Example
public class Student {
public final String name;
public Student() {
this.name = "Raju";
}
public Student(String name) {
this.name = name;
}
public void display() {
System.out.println("Name of the Student: "+this.name);
}
public static void main(String args[]) {
new Student().display();
new Student("Radha").display();
}
}Output
Name of the Student: Raju Name of the Student: Radha