Got confused with enumerations in java

[vinoth vino]

enum Student
{
 John(11), Bella(10), Sam(13), Viraaj(9);
 private int age;                   //age of students
 int getage { return age; }
 public Student(int age)
 {
  this.age= age;
 }
}

class EnumDemo
{
 public static void main( String args[] )
 {
  Student S;
  System.out.println("Age of Viraaj is " +Student.Viraaj.getage()+ "years");
 }
}

OUTPUT : Age of Viraaj is 9 years

Please anyone explain me about the flow of this program ? i know that the enumerations contains only constants.... But i don't know the flow of program.Please kindly help me to understand. Thanks in advance

[Simon Roberts]

You didn't post your code accurately.

1) line 5 can't compile as it declares a method without using parentheses
2) You can't have a public constructor in an enum

Also, this is a very poor design choice to use enum values to store information about people. Enums are intended for when the concept being modeled has a fixed number of values, and those values are known at compilation time. Suits of cards (Hearts, Diamonds...) are one of the classic examples.

That said, approximately what seems to be "supposed" to happen here is:

1) Main class will load
2) main method refers to the enum class, forcing it to load
3) loading the enum creates all instances that are defined by it, initializing them through their constructors using the provided arguments
4) main method is then able to complete access to sub-expression Student.Viraaj obtaining a reference to one of the enum elements
5) main continues evaluating the expression Student.Viraaj.getAge() by calling the method on the reference obtained in 4.

HTH
Simon

[vinoth vino]

vinoth vino wrote:

enum Student
{
 John(11), Bella(10), Sam(13), Viraaj(9);
 private int age;                   //age of students
 int getage { 
return age;
 }
 private Student(int age)
 {
  this.age= age;
 }
}

class EnumDemo
{
 public static void main( String args[] )
 {
  Student S;
  System.out.println("Age of Viraaj is " +Student.Viraaj.getage()+ "years");
 }
}

OUTPUT : Age of Viraaj is 9 years

Please anyone explain me about the flow of this program ? i know that the enumerations contains only constants.... But i don't know the flow of program.Please kindly help me to understand. Thanks in advance

[Mike. J. Thompson]

vinoth vino wrote:

enum Student
{
 John(11), Bella(10), Sam(13), Viraaj(9);
 private int age;                   //age of students
 int getage { return age; }
 public Student(int age)
 {
  this.age= age;
 }
}

class EnumDemo
{
 public static void main( String args[] )
 {
  Student S;
  System.out.println("Age of Viraaj is " +Student.Viraaj.getage()+ "years");
 }
}

OUTPUT : Age of Viraaj is 9 years

Please anyone explain me about the flow of this program ? i know that the enumerations contains only constants.... But i don't know the flow of program.Please kindly help me to understand. Thanks in advance

Firstly what you have there is an enum, not an enumeration. I make the distinction because there is a legacy Enumeration class in Java and it would be easy to get confused.

The flow is quite simple. When the Student enum is loaded by the classloader each of the enum members is created. Each one of those members calls the constructor for Student and supplies an age as parameter. The result is that the Student enum contains 4 different members each with a different age.

You then select one of the members and get its age by calling the getAge method, then print it out.

[vinoth vino]

I m learning this from studytonight site.In that site they declared public access modifiers in constructors is this wrong ? is enumerations will not accept puplic constructors ?

[vinoth vino]

vinoth vino wrote:

vinoth vino wrote:

enum Student
{
 John(11), Bella(10), Sam(13), Viraaj(9);
 private int age;                   //age of students
 int getage(){ 
return age;
 }
 private Student(int age)
 {
  this.age= age;
 }
}

class EnumDemo
{
 public static void main( String args[] )
 {
  Student S;
  System.out.println("Age of Viraaj is " +Student.Viraaj.getage()+ "years");
 }
}

OUTPUT : Age of Viraaj is 9 years

Please anyone explain me about the flow of this program ? i know that the enumerations contains only constants.... But i don't know the flow of program.Please kindly help me to understand. Thanks in advance

[Mike. J. Thompson]

Try and compile it and see what the compiler says.

[vinoth vino]

Is the variable also needs to be declared as private like constructors???