Java Fundamentals Tutorial: Additional Java Features

	Caution
	Most other Date methods are deprecated. They supported time and date manipulation, parsing, and formatting, but they have been superseded by newer classes.

The System.currentTimeMillis() returns the current epoch-based time as a long.

package util;

import java.util.Date;
import java.util.Calendar;
import java.util.TimeZone;

public class Now {
    public static void main(String[] args) {
        Date date = new Date();
        System.out.println(date);
        System.out.println(date.getTime() + " ms since the epoch");

        Calendar c = Calendar.getInstance();
        System.out.println("Year:   " + c.get(Calendar.YEAR));
        System.out.println("Month:  " + c.get(Calendar.MONTH));
        System.out.println("Day:    " + c.get(Calendar.DAY_OF_MONTH));
        System.out.println("WeekDay:" + c.get(Calendar.DAY_OF_WEEK));
        System.out.println("Hour:   " + c.get(Calendar.HOUR_OF_DAY));
        System.out.println("Minute: " + c.get(Calendar.MINUTE));
        System.out.println("Second: " + c.get(Calendar.SECOND));
        System.out.println("Millis: " + c.get(Calendar.MILLISECOND));

        TimeZone timeZone = c.getTimeZone();
        System.out.println("TZ ID:  " + timeZone.getID());
        System.out.println("TZ Name:" + timeZone.getDisplayName());
        System.out.println("TZ Off: " + timeZone.getRawOffset());
    }
}

package com.marakana.demo;

import java.util.Date;
import java.text.*;

public class DateExample {

    public static void main(String[] args) {
        Date now = new Date();
        DateFormat df;

        // Get the default date and time format
        df = DateFormat.getDateTimeInstance();
        System.out.println(df.format(now));

        // Get the default "short" date and time format
        df = DateFormat.getInstance();
        System.out.println(df.format(now));

        // Get the default "medium" date format
        df = DateFormat.getDateInstance(DateFormat.MEDIUM);
        System.out.println(df.format(now));

        // Get the default "long" time format
        df = DateFormat.getTimeInstance(DateFormat.LONG);
        System.out.println(df.format(now));

        // An example of parsing a time and date string into a Date
        try {
            df = new SimpleDateFormat("MMM d, y");
            Date birthday = df.parse("August 29, 1965");
            df = DateFormat.getDateInstance(DateFormat.MEDIUM);
            System.out.println(df.format(birthday));
        } catch (ParseException e) {
            // Couldn't parse the date string
            e.printStackTrace();
        }


    }

}

package com.marakana.demo;

import java.text.*;
import java.util.Locale;

public class FormatNumbers {

    public static void main(String[] args) {
        // Print out a number using the localized number, integer, currency,
         // and percent format for each locale
         Locale[] locales = NumberFormat.getAvailableLocales();
         double myNumber = -123456.78;
         NumberFormat form;
         for (int j=0; j<4; ++j) {
             System.out.println("FORMAT");
             for (Locale l: locales) {
                 if (l.getCountry().length() == 0) {
                    continue; // Skip language-only locales
                 }
                 System.out.print(l.getDisplayName());
                 switch (j) {
                 case 0:
                     form = NumberFormat.getInstance(l); break;
                 case 1:
                     form = NumberFormat.getIntegerInstance(l); break;
                 case 2:
                     form = NumberFormat.getCurrencyInstance(l); break;
                 default:
                     form = NumberFormat.getPercentInstance(l); break;
                 }
                 if (form instanceof DecimalFormat) {
                     System.out.print(":\t" + ((DecimalFormat) form).toPattern());
                 }
                 System.out.print(" ->\t" + form.format(myNumber));
                 try {
                     System.out.println(" ->\t" + form.parse(form.format(myNumber)));
                 } catch (ParseException e) {}
             }
         }
    }

}

public class ChessPiece {
    public static final int COLOR_WHITE = 0;
    public static final int COLOR_BLACK = 1;
    public static final int FIGURE_KING = 0;
    public static final int FIGURE_QUEEN = 1;
    public static final int FIGURE_ROOK = 2;
    public static final int FIGURE_BISHOP = 3;
    public static final int FIGURE_KNIGHT = 4;
    public static final int FIGURE_PAWN = 5;

    private final int color;
    private final int figure;

    public ChessPiece(int color, int figure) {
        this.color = color;
        this.figure = figure;
    }

    public int getColor() { return this.color; }
    public int getFigure() { return this.figure; }

    public String toString() {
        /* switch statements to convert int color and figure to string */
    }
}

But the following invalid initialization still compiles!

new ChessPiece(ChessPiece.FIGURE_QUEEN, ChessPiece.FIGURE_KING);

You can even combine int enums in unnatural ways:

int combined = ChessPiece.COLOR_BLACK + ChessPiece.FIGURE_PAWN;

	Tip
	Use enums any time you need a fixed set of constants. For example: choices on a menu, rounding modes, command line flags, etc.

public class ChessPiece {
  public static enum Figure {KING, QUEEN, ROOK, BISHOP, KNIGHT, PAWN};
  public static enum Color { WHITE, BLACK };

  private final Color color;
  private final Figure figure;

  public ChessPiece(Color color, Figure figure) {
    this.color = color;
    this.figure = figure;
  }

  public Figure getFigure() {
    return this.figure;
  }

  public Color getColor() {
    return this.color;
  }

  public String toString() {
    return this.color + " " + this.figure;
  }
}

The Java annotation facility consists of:

Annotation elements must be compile-time constant values.

Annotation elements may be primitive types, Strings, Classes, enums, annotations, or an array of a permitted type.

An array of values is supplied within braces, as in:

@SuppressWarnings({"unchecked","deprecation"})

The java.lang package defines three standard annotations: