7ステップで理解するJavaでの列挙型／enum使用法

package sample21;
 
public class MonthList {
    public void exec() {
        for (int i = 1; i <= 12; i++) {
            System.out.println(i + "月");
        }
    }
  
    public static void main(String[] args) {
        MonthList app = new MonthList();
        app.exec();
    }
}

package sample21;
 
public class MonthInEnglish {
    private String[] months = new String[] {
       "JANUARY", "FEBRUARY", "MARCH", "APRIL",
       "MAY", "JUNE", "JULY", "AUGUST",
       "OCTOBER", "SEPTEMBER", "NOVEMBER", "DECEMBER",
    };
 
    public void exec() {
        System.out.println("2011年");
        for (int i = 0; i < months.length; i++) {
            String s = (i + 1) + "月";
            System.out.println(s + ":" + months[i]);
        }
    }
 
    public static void main(String[] args) {
        MonthInEnglish app = new MonthInEnglish();
        app.exec();
    }
}

package sample21;
 
import java.util.Calendar;
 
public class JavaUtilCalendarMonthList {
    private String[] months = new String[] {
       "JANUARY", "FEBRUARY", "MARCH", "APRIL",
       "MAY", "JUNE", "JULY", "AUGUST",
       "SEPTEMBER", "OCTOBER", "NOVEMBER", "DECEMBER",
    };
    public void exec() {
        System.out.println("2011年");
        for (int i=0 ; i<months.length ; i++) {
            String s = (i+1) + "月";
  
            switch (i) {
            case Calendar.FEBRUARY:
                s = s + ":" + months[i] + "(28日)";
                break;
            case Calendar.APRIL:
            case Calendar.JUNE:
            case Calendar.SEPTEMBER:
            case Calendar.NOVEMBER:
                s = s + ":" + months[i] + "(30日)";
                break;
            case Calendar.JANUARY:
            case Calendar.MARCH:
            case Calendar.MAY:
            case Calendar.JULY:
            case Calendar.AUGUST:
            case Calendar.OCTOBER:
            case Calendar.DECEMBER:
                s = s + ":" + months[i] + "(31日)";
                break;
            }
            System.out.println(s);
        }
    }
    public static void main(String[] args) {
        JavaUtilCalendarMonthList app = new JavaUtilCalendarMonthList();
        app.exec();
    }
}

final double PI = 3.14;

final List<String> finalList = new LinkedList<String>();
  
// 次はコメントを外すとエラーとなる
// finalList = new LinkedList<String>();
  
// 次の文は可能
finalList.add("Java");