Java Tutorial/Data Type/enum methods

Adding Members to an Enumeration Class

enum JacketSize {
  small(36), medium(40), large(42), extra_large(46), extra_extra_large(48);
  JacketSize(int chestSize) {
    this.chestSize = chestSize;
  }
  public int chestSize() {
    return chestSize;
  }
  private int chestSize;
}
class Jacket {
  public Jacket(JacketSize size) {
    this.size = size;
  }
  public String toString() {
    switch (this.size) {
    case small:
      return "S";
    case medium:
      return "M";
    case large:
      return "L";
    case extra_large:
      return "XL";
    case extra_extra_large:
      return "XXL";
    default:
      return "";
    }
  }
  private JacketSize size;
}
public class MainClass {
  public static void main(String[] args) {
    Jacket[] jackets = { new Jacket(JacketSize.medium), 
                         new Jacket(JacketSize.extra_large),
                         new Jacket(JacketSize.small), 
                         new Jacket(JacketSize.extra_extra_large) };
    System.out.println("\n\nJackets sizes available are:\n");
    for (JacketSize size : JacketSize.values()) {
      System.out.print(" " + size);
    }
    System.out.println("\n\nJackets in stock are:");
    for (Jacket jacket : jackets) {
      System.out.println(jacket);
    }
  }
}

Jackets sizes available are:
 small medium large extra_large extra_extra_large
Jackets in stock are:
M
XL
S
XXL

compareTo() and equals() for enum data type

enum Week {
  Monday, Tuesday, Wednesday, Thursday, Friday, Saturaday, Sunday
}
public class MainClass {
  public static void main(String args[]) {
    Week day1, day2, day3;
    day1 = Week.Monday;
    day2 = Week.Tuesday;
    day3 = Week.Friday;
    // 
    if (day1.rupareTo(day2) < 0)
      System.out.println(day1 + " comes before " + day2);
    if (day2.rupareTo(day3) > 0)
      System.out.println(day2 + " comes before " + day3);
    if (day1.rupareTo(day3) == 0)
      System.out.println(day1 + " equals " + day3);
  }
}

Monday comes before Tuesday

Demonstrate ordinal(), compareTo(), and equals().

enum Apple {
  A, B, C, D, E
}
class EnumDemo4 {
  public static void main(String args[]) {
    Apple ap, ap2, ap3;
    for (Apple a : Apple.values())
      System.out.println(a + " " + a.ordinal());
    ap = Apple.C;
    ap2 = Apple.B;
    ap3 = Apple.C;
    System.out.println();
    if (ap.rupareTo(ap2) < 0)
      System.out.println(ap + " comes before " + ap2);
    if (ap.rupareTo(ap2) > 0)
      System.out.println(ap2 + " comes before " + ap);
    if (ap.rupareTo(ap3) == 0)
      System.out.println(ap + " equals " + ap3);
    System.out.println();
    if (ap.equals(ap2))
      System.out.println("Error!");
    if (ap.equals(ap3))
      System.out.println(ap + " equals " + ap3);
    if (ap == ap3)
      System.out.println(ap + " == " + ap3);
  }
}

Obtaining all ordinal values using ordinal()

enum Week {
  Monday, Tuesday, Wednesday, Thursday, Friday, Saturaday, Sunday
}
public class MainClass {
  public static void main(String args[]) {
    // Obtain all ordinal values using ordinal().
    System.out.println("Here are all week constants" + " and their ordinal values: ");
    for (Week day : Week.values())
      System.out.println(day + " " + day.ordinal());
  }
}

Here are all week constants and their ordinal values: 
Monday 0
Tuesday 1
Wednesday 2
Thursday 3
Friday 4
Saturaday 5
Sunday 6

Switch statement with enum

public class MainClass {
  enum Choice { Choice1, Choice2, Choice3 }
  public static void main(String[] args) {
    Choice ch = Choice.Choice1;
    switch(ch) {
      case Choice1:
        System.out.println("Choice1 selected");
        break;
     case Choice2:
       System.out.println("Choice2 selected");
       break;
     case Choice3:
       System.out.println("Choice3 selected");
       break;
    }
  }
}

Choice1 selected

Use an enum constructor, instance variable, and method.

enum Apple {
  A(10), B(9), C(12), D(15), E(8);
  private int price; // price of each apple
  Apple(int p) {
    price = p;
  }
  int getPrice() {
    return price;
  }
}
class EnumDemo3 {
  public static void main(String args[]) {
    Apple ap;
    System.out.println("D costs " + Apple.D.getPrice() + " cents.\n");
    System.out.println("All apple prices:");
    for (Apple a : Apple.values())
      System.out.println(a + " costs " + a.getPrice() + " cents.");
  }
}

Use the built-in enumeration methods.

enum Apple {
  A, B, C, D, E
}
class EnumDemo2 {
  public static void main(String args[]) {
    Apple ap;
    System.out.println("Here are all Apple constants:");
    // use values()
    Apple allapples[] = Apple.values();
    for (Apple a : allapples)
      System.out.println(a);
    System.out.println();
    // use valueOf()
    ap = Apple.valueOf("D");
    System.out.println("ap contains " + ap);
  }
}

Using the built-in enumeration methods: values( )

All enumerations automatically contain two predefined methods: values( ) and valueOf( ).

1. public static enum-type[ ] values( )
2. public static enum-type valueOf(String str)

The values( ) method returns an array that contains a list of the enumeration constants.

The valueOf( ) method returns the enumeration constant whose value corresponds to the string passed in str.

enum Week {
  Monday, Tuesday, Wednesday, Thursday, Friday, Saturaday, Sunday
}
public class MainClass {
  public static void main(String args[]) {
    System.out.println("Here are all Week constants");
    // use values()
    Week allWeek[] = Week.values();
    for (Week aday : allWeek) {
      System.out.println(aday);
    }
  }
}

Here are all Week constants
Monday
Tuesday
Wednesday
Thursday
Friday
Saturaday
Sunday

Using valueOf()

enum Week {
  Monday, Tuesday, Wednesday, Thursday, Friday, Saturaday, Sunday
}
public class MainClass {
  public static void main(String args[]) {
    Week day;
    // 
    day = Week.valueOf("Monday");
    System.out.println("day contains " + day);
  }
}

day contains Monday