Java

This is a printer-friendly version. It omits exercises, optional topics (i.e., four-star topics), and other extra content such as learning outcomes.

Collections

Enums

You can define an enum type by using the enum keyword. Because they are constants, the names of an enum type's fields are in uppercase letters e.g., FLAG_SUCCESS.

Defining an enumeration to represent days of a week (code to be put in the Day.java file):

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

Some examples of using the Day enumeration defined above:

Day today = Day.MONDAY;
Day[] holidays = new Day[]{Day.SATURDAY, Day.SUNDAY};

switch (today) {
case SATURDAY:
case SUNDAY:
    System.out.println("It's the weekend");
    break;
default:
    System.out.println("It's a week day");
}

Note that while enumerations are usually a simple set of fixed values, Java enumerations can have behaviors too, as explained in this tutorial from -- Java Tutorial