Write a note on ordinal() and compareTo()

2.C] Write a note on:
i) ordinal()
ii) compareTo()

Answer:

In Java, both ordinal() and compareTo() methods are commonly used with enumerations (enum) but can also be applied in other contexts. Here’s a detailed explanation of each:

i) ordinal()

• The ordinal() method returns the position of an enum constant in its enum declaration. The first constant is assigned an ordinal value of 0, the second 1, and so on. This method is useful when you need to know the order of constants within an enum.
• Syntax:

  enumName.constantName.ordinal()

• Example:

  enum Day {
      SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY
  }

  public class OrdinalExample {
      public static void main(String[] args) {
          Day day = Day.WEDNESDAY;
          System.out.println("The ordinal of " + day + " is: " + day.ordinal());
      }
  }

• Output:

  The ordinal of WEDNESDAY is: 3

• In the example above, WEDNESDAY is the fourth constant in the enum Day, so its ordinal value is 3.

ii) compareTo()

• The compareTo() method is used to compare the ordinal values of two enum constants. It returns:
• 0 if the two enum constants are the same.
• A negative integer if the current enum constant’s ordinal is less than the compared enum constant’s ordinal.
• A positive integer if the current enum constant’s ordinal is greater than the compared enum constant’s ordinal.
• Syntax:

  enumName.constantName1.compareTo(enumName.constantName2)

• Example:

  enum Day {
      SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY
  }

  public class CompareToExample {
      public static void main(String[] args) {
          Day day1 = Day.MONDAY;
          Day day2 = Day.WEDNESDAY;
          int result = day1.compareTo(day2);

          if (result == 0) {
              System.out.println(day1 + " is equal to " + day2);
          } else if (result < 0) {
              System.out.println(day1 + " comes before " + day2);
          } else {
              System.out.println(day1 + " comes after " + day2);
          }
      }
  }

• Output:

  MONDAY comes before WEDNESDAY

• In this example, MONDAY has an ordinal value of 1 and WEDNESDAY has an ordinal value of 3. Since 1 < 3, the compareTo() method returns a negative integer, indicating that MONDAY comes before WEDNESDAY.

Summary:

• ordinal() provides the position of an enum constant within the enum declaration.
• compareTo() compares the ordinal values of two enum constants to determine their order relative to each other.

These methods are particularly useful for managing and organizing enums in Java.