Declare Constants

Note : Use enum instead of 'public static final String variable '
=========

import java.io.Serializable;
import java.util.HashMap;

enum UserCredential{
    LOGIN, PASSWORD, TOKEN, USERNAME;
}
public class TestClass1 {


    public static void main(String[] args){

        System.out.println("--------Hello---------");

        System.out.println("--------"+UserCredential.LOGIN+"---------");

        HashMap<UserCredential, String> map = new HashMap();
        map.put(UserCredential.LOGIN, "India");
        System.out.println("--------"+map.get(UserCredential.LOGIN)+"---------");
        
        
    }
}

============== =========== ======== ====== ====

Enums in java are mainly used for grouping similar kind of constants as a one unit. constants means static and final. Enums are introduced in JDK 1.5 onward. Before that similar kind of constants are grouped by declaring them as static and final in one class. Below example shows how the constants will look without enums.

class ConstantsWithoutEnums
{
 public static final String north = "NORTH";
 public static final String south = "SOUTH";
 public static final String east = "EAST";
 public static final String west = "WEST";
}

public class MainClass
{
 public static void main(String[] args)
 {
  System.out.println(ConstantsWithoutEnums.north);
  System.out.println(ConstantsWithoutEnums.south);
  System.out.println(ConstantsWithoutEnums.east);
  System.out.println(ConstantsWithoutEnums.west);
 }
}

Above constatnts can be defined with enums as below,

enum Directions
{
 NORTH, SOUTH, EAST, WEST;
}

public class EnumsExample
{
 public static void main(String[] args)
 {
  Directions d1 = Directions.EAST;
  System.out.println(d1);

  Directions d2 = Directions.NORTH;
  System.out.println(d2);

  System.out.println(Directions.SOUTH);

  System.out.println(Directions.WEST);
 }
}

22