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java.util.Date

Earlier in this tutorial we examined log files using RandomAccessFile. Now is a good time to re-visit log
files and add timestamps to our log files, so we can keep track of when certain events occurred.

In the following example, we will keep track of the purchases happening at a hot dog stand. We will output
the time when sales are made in the format of milliseconds since Unix epoch which is January 1, 1970.

Here is the example:
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.*;
import java.util.Date;

class HotDogMilliseconds extends Frame
implements ActionListener {
  double dblCostFlat=0.0d;
  double dblCostPer=0.0d;
  double dblRevenuePer=0.0d;
  double dblProfitPer=0.0d;
  String strLogFilePath="";

  TextField txtNumberOfHotDogs=new TextField();
  TextField txtYear=new TextField();
  TextField txtMonth=new TextField();
  TextField txtDate=new TextField();
  TextField txtHour=new TextField();
  Button btnSold=new Button("Sold");

  TextArea txtStatus=new TextArea();
  Button btnStatistics=new Button("Statistics");

  public static void main(String args[]) {
    try {
      if(args.length==0) {
        System.out.println("Usage:");
        System.out.println("  java HotDogMilliseconds <flat cost> <per hot dog cost> <per hot dog revenue> <log file path>");
        System.out.println("OR");
        System.out.println("  java HotDogMilliseconds <existing log file path>");

        return;
      }

      if(args.length==4) {
        double dblCostFlat=Double.valueOf(args[0]).doubleValue();
        double dblCostPer=Double.valueOf(args[1]).doubleValue();
        double dblRevenuePer=Double.valueOf(args[2]).doubleValue();
        String strLogFilePath=args[3];

        HotDogMilliseconds hFrame=new HotDogMilliseconds(dblCostFlat, dblCostPer, dblRevenuePer, strLogFilePath);
        Dimension dimScreen=Toolkit.getDefaultToolkit().getScreenSize();
        hFrame.setSize(dimScreen.width, dimScreen.height-40);
        hFrame.setVisible(true);
      }
      else if(args.length==1) {
        String strLogFilePath=args[0];

        BufferedReader br=new BufferedReader(new InputStreamReader(new FileInputStream(new File(strLogFilePath))));

        String strCostAndRevenue=br.readLine();

        int intSeparatorIndex=strCostAndRevenue.indexOf(",");
        int intSeparatorIndex2=strCostAndRevenue.indexOf(",", intSeparatorIndex+1);

        String strCostFlat=strCostAndRevenue.substring(0, intSeparatorIndex);
        String strCostPer=strCostAndRevenue.substring(intSeparatorIndex+1, intSeparatorIndex2);
        String strRevenuePer=strCostAndRevenue.substring(intSeparatorIndex2+1);

        double dblCostFlat=Double.valueOf(strCostFlat).doubleValue();
        double dblCostPer=Double.valueOf(strCostPer).doubleValue();
        double dblRevenuePer=Double.valueOf(strRevenuePer).doubleValue();

        HotDogMilliseconds hFrame=new HotDogMilliseconds(dblCostFlat, dblCostPer, dblRevenuePer, strLogFilePath);
        Dimension dimScreen=Toolkit.getDefaultToolkit().getScreenSize();
        hFrame.setSize(dimScreen.width, dimScreen.height-40);
        hFrame.setVisible(true);

//Skip over the second line in the file because the first two lines don't have transaction data.
        br.readLine();

        String strNextLine="";
        while((strNextLine=br.readLine())!=null) {
          intSeparatorIndex=strNextLine.indexOf(",");

          String strNumberOfHotDogs=strNextLine.substring(0, intSeparatorIndex);

          String strMilliseconds=strNextLine.substring(intSeparatorIndex+1);

          Date datePurchased=new Date(Long.valueOf(strMilliseconds).longValue());

          String strTransaction=strNumberOfHotDogs+","+String.valueOf(datePurchased);

          hFrame.txtStatus.append(strTransaction+"\n");
        }

        br.close();
      }
    }
    catch(Exception ex) {
      ex.printStackTrace();
    }
  }

  HotDogMilliseconds(double dblCostFlat, double dblCostPer, double dblRevenuePer, String strLogFilePath) {
    super("Hot Dog Shop");
    this.dblCostFlat=dblCostFlat;
    this.dblCostPer=dblCostPer;
    this.dblRevenuePer=dblRevenuePer;
    this.dblProfitPer=dblRevenuePer-dblCostPer;
    this.strLogFilePath=strLogFilePath;

    setIconImage(new BufferedImage(1, 1, BufferedImage.TYPE_INT_RGB));
    addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent we) {
        System.exit(0);
      }
    });

    Panel tempPan=new Panel();
    tempPan.setLayout(new GridLayout(7, 1));
    Panel tempPanA=new Panel();
    tempPanA.setLayout(new GridLayout(1, 2));
    tempPanA.add(new Label("Number of Hot Dogs Sold:"));
    tempPanA.add(txtNumberOfHotDogs);
    tempPan.add(tempPanA);
    Panel tempPanB=new Panel();
    tempPanB.setLayout(new GridLayout(1, 2));
    tempPanB.add(new Label("Year:"));
    tempPanB.add(txtYear);
    tempPan.add(tempPanB);
    Panel tempPanC=new Panel();
    tempPanC.setLayout(new GridLayout(1, 2));
    tempPanC.add(new Label("Month(0-11):"));
    tempPanC.add(txtMonth);
    tempPan.add(tempPanC);
    Panel tempPanD=new Panel();
    tempPanD.setLayout(new GridLayout(1, 2));
    tempPanD.add(new Label("Day(1-31):"));
    tempPanD.add(txtDate);
    tempPan.add(tempPanD);
    Panel tempPanE=new Panel();
    tempPanE.setLayout(new GridLayout(1, 2));
    tempPanE.add(new Label("Hour(0-23):"));
    tempPanE.add(txtHour);
    tempPan.add(tempPanE);
    Panel tempPanF=new Panel();
    tempPanF.add(btnSold);
    btnSold.addActionListener(this);
    tempPan.add(tempPanF);
    tempPan.add(new Label("Status:"));

    add("North", tempPan);

    add("Center", txtStatus);

    Panel tempPan2=new Panel();
    tempPan2.add(btnStatistics);
    btnStatistics.addActionListener(this);

    add("South", tempPan2);
  }

  public void actionPerformed(ActionEvent ae) {
    Object evSource=ae.getSource();

    if(evSource==btnSold) {
      String strNumberOfHotDogs=txtNumberOfHotDogs.getText();
      if(strNumberOfHotDogs.length()==0) {
        txtNumberOfHotDogs.setText("Number required.");
        try {
          Thread.sleep(3000);
        }
        catch(Exception ex) {
        }
        txtNumberOfHotDogs.setText("");

        return;
      }

      int intNumberOfHotDogs=-1;
      try {
        intNumberOfHotDogs=Integer.parseInt(strNumberOfHotDogs);
      }
      catch(Exception ex) {
        txtNumberOfHotDogs.setText("Digits only required.");
        try {
          Thread.sleep(3000);
        }
        catch(Exception ex2) {
        }
        txtNumberOfHotDogs.setText(strNumberOfHotDogs);

        return;
      }

      if(intNumberOfHotDogs<1 || intNumberOfHotDogs>20) {
        txtNumberOfHotDogs.setText("Number must be between 1-20.");
        try {
          Thread.sleep(3000);
        }
        catch(Exception ex2) {
        }
        txtNumberOfHotDogs.setText(strNumberOfHotDogs);

        return;
      }

      Date dateNow=new Date();

      int intYear=-1;
      String strYear=txtYear.getText();
      if(strYear.length()==0) {
        intYear=dateNow.getYear()+1900;
      }
      else {
        try {
          intYear=Integer.parseInt(strYear);
        }
        catch(Exception ex) {
          txtYear.setText("Digits only required.");
          try {
            Thread.sleep(3000);
          }
          catch(Exception ex2) {
          }
          txtYear.setText(strYear);

          return;
        }
      }


      int intMonth=-1;
      String strMonth=txtMonth.getText();
      if(strMonth.length()==0) {
        intMonth=dateNow.getMonth();
      }
      else {
        try {
          intMonth=Integer.parseInt(strMonth);
        }
        catch(Exception ex) {
          txtMonth.setText("Digits only required.");
          try {
            Thread.sleep(3000);
          }
          catch(Exception ex2) {
          }
          txtMonth.setText(strMonth);

          return;
        }

        if(intMonth<0 || intMonth>11) {
          txtMonth.setText("Number must be between 0-11.");
          try {
            Thread.sleep(3000);
          }
          catch(Exception ex2) {
          }
          txtMonth.setText(strMonth);

          return;
        }
      }


      int intDate=-1;
      String strDate=txtDate.getText();
      if(strDate.length()==0) {
        intDate=dateNow.getDate();
      }
      else {
        try {
          intDate=Integer.parseInt(strDate);
        }
        catch(Exception ex) {
          txtDate.setText("Digits only required.");
          try {
            Thread.sleep(3000);
          }
          catch(Exception ex2) {
          }
          txtDate.setText(strDate);

          return;
        }

        if(intDate<1 || intDate>31) {
          txtDate.setText("Number must be between 1-31.");
          try {
            Thread.sleep(3000);
          }
          catch(Exception ex2) {
          }
          txtDate.setText(strDate);

          return;
        }
      }


      int intHour=-1;
      String strHour=txtHour.getText();
      if(strHour.length()==0) {
        intHour=dateNow.getHours();
      }
      else {
        try {
          intHour=Integer.parseInt(strHour);
        }
        catch(Exception ex) {
          txtHour.setText("Digits only required.");
          try {
            Thread.sleep(3000);
          }
          catch(Exception ex2) {
          }
          txtHour.setText(strHour);

          return;
        }

        if(intHour<0 || intHour>23) {
          txtHour.setText("Number must be between 0-23.");
          try {
            Thread.sleep(3000);
          }
          catch(Exception ex2) {
          }
          txtHour.setText(strHour);

          return;
        }
      }

      Date datePurchased=new Date(intYear-1900, intMonth, intDate, intHour, 0);

      try {
        File fileLog=new File(strLogFilePath);
        if(!fileLog.exists()) {
          fileLog.createNewFile();

          RandomAccessFile raf=new RandomAccessFile(fileLog, "rw");

          raf.writeBytes(String.valueOf(dblCostFlat));
          raf.writeBytes(",");
          raf.writeBytes(String.valueOf(dblCostPer));
          raf.writeBytes(",");
          raf.writeBytes(String.valueOf(dblRevenuePer));

          raf.write(13);
          raf.write(10);
          raf.write(13);
          raf.write(10);

          raf.close();
        }

        RandomAccessFile raf=new RandomAccessFile(fileLog, "rw");
        raf.seek(fileLog.length());

        String strTransaction=strNumberOfHotDogs+","+String.valueOf(datePurchased.getTime());

        raf.writeBytes(strTransaction);
        raf.write(13);
        raf.write(10);

        raf.close();

        strTransaction=strNumberOfHotDogs+","+String.valueOf(datePurchased);

        txtStatus.append(strTransaction+"\n");
      }
      catch(Exception ex) {
        txtStatus.append(String.valueOf(ex)+"\n");
      }
    }
    else if(evSource==btnStatistics) {
      File fileLog=new File(strLogFilePath);
      if(!fileLog.exists()) {
        return;
      }

      try {
        BufferedReader br=new BufferedReader(new InputStreamReader(new FileInputStream(fileLog)));

//Skip over the first two lines in the file because those lines don't have transaction data.
        br.readLine();
        br.readLine();

        int intSeparatorIndex=-1;
        int intNumberOfHotDogs=-1;
        double dblNumberOfHotDogsAccumulated=0.0d;
        int intNumberOfHotDogsHours[]=new int[24];
        for(int i=0;i<intNumberOfHotDogsHours.length;i++)
          intNumberOfHotDogsHours[i]=0;

        String strNextLine="";
        while((strNextLine=br.readLine())!=null) {
          intSeparatorIndex=strNextLine.indexOf(",");
          String strNumberOfHotDogs=strNextLine.substring(0, intSeparatorIndex);
          String strMilliseconds=strNextLine.substring(intSeparatorIndex+1);

          intNumberOfHotDogs=Integer.parseInt(strNumberOfHotDogs);
          dblNumberOfHotDogsAccumulated+=((double)intNumberOfHotDogs);

          Date dateNext=new Date(Long.valueOf(strMilliseconds).longValue());

          intNumberOfHotDogsHours[dateNext.getHours()]+=intNumberOfHotDogs;
        }

        br.close();


        String strNumberSold="Number of Hot Dogs Sold: "+String.valueOf(((int)Math.rint(dblNumberOfHotDogsAccumulated)));
        double dblProfit=dblProfitPer*dblNumberOfHotDogsAccumulated-dblCostFlat;

        dblProfit*=100.0d;
        dblProfit=Math.floor(dblProfit);
        dblProfit/=100.0d;

        String strProfit="Profit: $"+String.valueOf(dblProfit);

        String strNumberOfHotDogsHours[]=new String[24];
        for(int i=0;i<strNumberOfHotDogsHours.length;i++)
          strNumberOfHotDogsHours[i]=String.valueOf(intNumberOfHotDogsHours[i]);

        StatisticsDisplayerDialog sDialog=new StatisticsDisplayerDialog(this, strNumberSold, strProfit, strNumberOfHotDogsHours);
        sDialog.show();
      }
      catch(Exception ex) {
        ex.printStackTrace();
      }
    }
  }

  class StatisticsDisplayerDialog extends Dialog
  implements ActionListener {
    Button btnClose=new Button("Close");

    StatisticsDisplayerDialog(Frame parent, String strNumberSold, String strProfit, String strNumberOfHotDogsHours[]) {
      super(parent, "Statistics Displayer Dialog", true);

      Panel tempPan=new Panel();
      tempPan.setLayout(new GridLayout(27, 1));
      tempPan.add(new Label(strNumberSold));
      tempPan.add(new Label(strProfit));
      tempPan.add(new Label("Number Sold in Each Hour:"));
      for(int i=0;i<strNumberOfHotDogsHours.length;i++) {
        tempPan.add(new Label(String.valueOf(i)+": "+strNumberOfHotDogsHours[i]));
      }

      add("North", tempPan);

      add("Center", new Label(""));

      Panel tempPan2=new Panel();
      tempPan2.add(btnClose);
      btnClose.addActionListener(this);

      add("South", tempPan2);

      Dimension dimScreen=Toolkit.getDefaultToolkit().getScreenSize();
      setLocation(dimScreen.width/4, 0);
      setSize(dimScreen.width/2, dimScreen.height-40);
    }

    public void actionPerformed(ActionEvent ae) {
      Object evSource=ae.getSource();

      if(evSource==btnClose) {
        dispose();
      }
    }
  }
}


Scroll down to "Date dateNow=new Date();" that is where we parse our Date object. We create the "dateNow"
field because we are going to fill in the data using "dateNow" if the user leaves a field blank.

When parsing the year, notice how we "+1900" this is because the Date object constructor expects a year
minus 1900 and we don't want the user to have to do the subtraction themselves. Let the "intYear"
equal the absolute year.

The month must be an int from 0-11, so we include a note about those constraints in the label next
to the TextField for the month.

The day must be an int from 1-31, so we include a note about those constraints in the label next
to the TextField for the day.

The hour must be an int from 0-23, so we include a note about those constraints in the label next
to the TextField for the hour.

The "datePurchased" Date object is the date that the user entered for the sale of hot dogs.

If the "fileLog" File doesn't exist we create one and add the user specified command line argument
information to the beginning of the file. This information is used later on if the user decides
to execute the HotDogMilliseconds.class with only one command line argument.

When we declare the "strTransaction" String we use the "datePurchased" Date's "getTime" function
to return the number of milliseconds from Unix epoch time corresponding to the "datePurchased"
variable. The number of milliseconds is written to the "fileLog" File.

Scroll down to "Date dateNext=", this is where we read in the milliseconds written to the log
file. The milliseconds read in is converted to a Date object by using one of Date object's
constructors; the constructor with only a single parameter, a long specifying the milliseconds
from Unix epoch.

The "dateNext" variable is then used to get the number of hours into the day the Date is which
is an int from 0-23. That number of hours is used as an index into our "intNumberOfHotDogsHours"
int array for accumulating the number of hot dogs sold on the given hour.

All of the rest of the code is similar to other lessons taught in this tutorial.

Try using this program with the following scenario:

A hot dog salesman has a monthly rent of $1000 and pays 50 cents for each hot dog and sells
each hot dog for 1 dollar. Execute the following command:
java HotDogMilliseconds 1000 0.50 1.0 HotDogLog.txt

Later on, if you want close the program and want to re-open the program using the same log file
then execute the following command:
java HotDogMilliseconds HotDogLog.txt

In this lesson, you learned how to use the Date object and its "getTime" method to convert
back and forth between Date objects and long milliseconds from Unix epoch time.