Hey,buddy:What's up?

本程序改变自网上的一个datapicker，没有用javax包，而是基于java.awt包。you can use it in your applet.共四个文件。

//1.AbsoluteConstraints.java

import java.awt.Dimension;
import java.awt.Point;

public class AbsoluteConstraints
    implements java.io.Serializable {
  static final long serialVersionUID = 5261460716622152494L;
  public int x;
  public int y;
  public int width = -1;
  public int height = -1;
  public AbsoluteConstraints(Point pos) {
    this(pos.x, pos.y);
  }

  public AbsoluteConstraints(int x, int y) {
    this.x = x;
    this.y = y;
  }

  public AbsoluteConstraints(Point pos, Dimension size) {
    this.x = pos.x;
    this.y = pos.y;
    if (size != null) {
      this.width = size.width;
      this.height = size.height;
    }
  }

  public AbsoluteConstraints(int x, int y, int width, int height) {
    this.x = x;
    this.y = y;
    this.width = width;
    this.height = height;
  }

  public int getX() {
    return x;
  }

  public int getY() {
    return y;
  }

  public int getWidth() {
    return width;
  }

  public int getHeight() {
    return height;
  }

  public String toString() {
    return super.toString() + " [x=" + x + ", y=" + y + ", width=" + width +
        ", height=" + height + "]";
  }
}



//2.import java.awt.*;

public class AbsoluteLayout
    implements LayoutManager2, java.io.Serializable {
  static final long
      serialVersionUID = -1919857869177070440L;
  protected java.util.Hashtable constraints = new java.util.Hashtable();
  public
      void addLayoutComponent(String name, Component comp) {
    throw new IllegalArgumentException();
  }

  public void
      removeLayoutComponent(Component comp) {
    constraints.remove(comp);
  }

  public Dimension preferredLayoutSize
      (Container parent) {
    int maxWidth = 0;
    int maxHeight = 0;
    for (java.util.Enumeration e =
         constraints.keys(); e.hasMoreElements(); ) {
      Component comp = (Component) e.nextElement();
      AbsoluteConstraints
          ac = (AbsoluteConstraints) constraints.get(comp);
      Dimension size = comp.getPreferredSize();
      int width =
          ac.getWidth();
      if (width == -1)
        width = size.width;
      int height = ac.getHeight();
      if (height == -1)
        height = size.height;
      if (ac.x + width > maxWidth)
        maxWidth = ac.x + width;
      if (ac.y + height >
          maxHeight)
        maxHeight = ac.y + height;
    }
    return new Dimension(maxWidth, maxHeight);
  }

  public
      Dimension minimumLayoutSize(Container parent) {
    int maxWidth = 0;
    int maxHeight = 0;
    for
        (java.util.Enumeration e = constraints.keys(); e.hasMoreElements(); ) {
      Component comp = (Component) e.nextElement();
      AbsoluteConstraints ac = (AbsoluteConstraints) constraints.get(comp);
      Dimension size = comp.getMinimumSize();
      int width = ac.getWidth();
      if (width == -1)
        width = size.width;
      int height = ac.getHeight();
      if (height == -1)
        height = size.height;
      if (ac.x + width > maxWidth)
        maxWidth = ac.x + width;
      if
          (ac.y + height > maxHeight)
        maxHeight = ac.y + height;
    }
    return new Dimension(maxWidth, maxHeight);
  }

  public void layoutContainer(Container parent) {
    for (java.util.Enumeration e = constraints.keys();
         e.hasMoreElements(); ) {
      Component comp = (Component) e.nextElement();
      AbsoluteConstraints ac =
          (AbsoluteConstraints) constraints.get(comp);
      Dimension size = comp.getPreferredSize();
      int width = ac.getWidth();
      if (width == -1)
        width = size.width;
      int height = ac.getHeight();
      if (height == -1)
        height = size.height;
      comp.setBounds(ac.x, ac.y, width, height);
    }
  }

  public void addLayoutComponent
      (Component comp, Object constr) {
    if (! (constr instanceof AbsoluteConstraints))
      throw new
          IllegalArgumentException();
    constraints.put(comp, constr);
  }

  public Dimension maximumLayoutSize(Container
                                     target) {
    return new Dimension(Integer.MAX_VALUE, Integer.MAX_VALUE);
  }

  public float getLayoutAlignmentX
      (Container target) {
    return 0;
  }

  public float getLayoutAlignmentY(Container target) {
    return 0;
  }

  public void invalidateLayout(Container target) {}
}

// 3DateField.java

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Insets;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.net.URL;
import java.text.DateFormat;
import java.text.ParseException;
import java.util.Date;
import java.awt.*;

public final class DateField
    extends Panel {
  private static final long serialVersionUID = 1L;
  private final TextField dateText = new TextField(12);
  private final Button dropdownButton = new Button();
  private DatePicker dp;
  private Dialog dlg;
  Point origin = new Point();
  final class Listener
      extends ComponentAdapter {
    public void componentHidden(final ComponentEvent evt) {
      final Date dt = ( (DatePicker) evt.getSource()).getDate();
      if (null != dt)
        dateText.setText(dateToString(dt));
      dlg.dispose();
    }
  }

  public DateField() {
    super();
    init();
  }

  public DateField(final Date initialDate) {
    super();
    init();
    dateText.setText(dateToString(initialDate));
  }

  public Date getDate() {
    return stringToDate(dateText.getText());
  }

  public void setDate(Date date) {
    String v = dateToString(date);
    if (v == null) {
      v = "";
    }
    dateText.setText(v);
  }

  private void init() {
    setLayout(new BorderLayout());
    dateText.setText("");
    dateText.setEditable(false);
    dateText.setBackground(new Color(255, 255, 255));
    add(dateText, BorderLayout.CENTER);
    dropdownButton.setLabel("选择");
    dropdownButton.setBackground(Color.yellow);
    dropdownButton.addActionListener(new ActionListener() {
      public void actionPerformed(final ActionEvent evt) {
        onButtonClick(evt);
      }
    });
    add(dropdownButton, BorderLayout.EAST);
  }

  private void onButtonClick(final java.awt.event.ActionEvent evt) {
    if ("".equals(dateText.getText()))
      dp = new DatePicker();
    else
      dp = new DatePicker(stringToDate(dateText.getText()));
    dp.addComponentListener(new Listener());
    final Point p = dateText.getLocationOnScreen();
    p.setLocation(p.getX(), p.getY() - 1 + dateText.getSize().getHeight());
    dlg = new Dialog(new Frame(), true);
    dlg.addMouseListener(new MouseAdapter() {
      public void mousePressed(MouseEvent e) {
        origin.x = e.getX();
        origin.y = e.getY();
      }
    });
    dlg.addMouseMotionListener(new MouseMotionAdapter() {
      public void mouseDragged(MouseEvent e) {
        Point p = dlg.getLocation();
        dlg.setLocation(p.x + e.getX() - origin.x, p.y + e.getY() - origin.y);
      }
    });
    dlg.setLocation(p);
    dlg.setResizable(false);
    dlg.setUndecorated(true);
    dlg.add(dp);
    dlg.pack();
    dlg.setVisible(true);
  }

  private static String dateToString(final Date dt) {
    if (null != dt)
      return DateFormat.getDateInstance(DateFormat.LONG).format(dt);
    return null;
  }

  private static Date stringToDate(final String s) {
    try {
      return DateFormat.getDateInstance(DateFormat.LONG).parse(s);
    }
    catch (ParseException e) {
      return null;
    }
  }

  public static void main(String[] args) {
    Dialog dlg = new Dialog(new Frame(), true);
    DateField df = new DateField();
   //dlg.getContentPane().add(df);
   dlg.add(df);
    dlg.pack();
    dlg.setVisible(true);
    System.out.println(df.getDate().toString());
    System.exit(0);
  }
}

//4.DatePicker.java

import java.awt.*;
import java.awt.event.*;
import java.util.GregorianCalendar;
import java.util.Date;
import java.util.Calendar;
import java.text.DateFormat;
import java.text.FieldPosition;
/*
import javax.swing.*;
import javax.swing.plaf.BorderUIResource;
*/
public final class DatePicker
    extends Panel {
  private static final long serialVersionUID = 1L;
  private static final int startX = 10;
  private static final int startY = 60;
  private static final Font smallFont = new Font("Dialog", Font.PLAIN, 10);
  private static final Font largeFont = new Font("Dialog", Font.PLAIN, 12);
  private static final Insets insets = new Insets(2, 2, 2, 2);
  private static final Color highlight = Color.YELLOW;//new Color(255, 255, 204);
  private static final Color white = new Color(255, 255, 255);
  private static final Color gray = new Color(204, 204, 204);
  private Component selectedDay = null;
  private GregorianCalendar selectedDate = null;
  private GregorianCalendar originalDate = null;
  private boolean hideOnSelect = true;
  private final Button backButton = new Button();
  private final Label monthAndYear = new Label();
  private final Button forwardButton = new Button();
  private final Label[] dayHeadings = new Label[] {
      new Label("日"),
      new Label("一"),
      new Label("二"),
      new Label("三"),
      new Label("四"),
      new Label("五"),
      new Label("六")};

  private final Label[][] daysInMonth = new Label[][] {
      {
      new Label(), new Label(),
      new Label(), new Label(),
      new Label(), new Label(),
      new Label()}
      , {
      new Label(),
      new Label(), new Label(),
      new Label(), new Label(),
      new Label(), new Label()}
      , {
      new Label(), new Label(),
      new Label(), new Label(),
      new Label(), new Label(),
      new Label()}
      , {
      new Label(),
      new Label(), new Label(),
      new Label(), new Label(),
      new Label(), new Label()}
      , {
      new Label(), new Label(),
      new Label(), new Label(),
      new Label(), new Label(),
      new Label()}
      , {
      new Label(),
      new Label(), new Label(),
      new Label(), new Label(),
      new Label(), new Label()}
  };
  private final Button todayButton = new Button();
  private final Button cancelButton = new Button();
  public DatePicker() {
    super();
    selectedDate = getToday();
    init();
  }

  public DatePicker(final Date initialDate) {
    super();
    if (null == initialDate)
      selectedDate = getToday();
    else
      (selectedDate = new GregorianCalendar()).setTime(initialDate);
    originalDate = new GregorianCalendar(selectedDate.get(Calendar.YEAR),
                                         selectedDate.get(Calendar.MONTH),
                                         selectedDate.get(Calendar.DATE));
    init();
  }

  public boolean isHideOnSelect() {
    return hideOnSelect;
  }

  public void setHideOnSelect(final boolean hideOnSelect) {
    if (this.hideOnSelect != hideOnSelect) {
      this.hideOnSelect = hideOnSelect;
      initButtons(false);
    }
  }

  public Date getDate() {
    if (null != selectedDate)
      return selectedDate.getTime();
    return null;
  }

  private void init() {
    setLayout(new AbsoluteLayout());
    /*
    this.setMinimumSize(new Dimension(161, 226));
    this.setMaximumSize(getMinimumSize());
    this.setPreferredSize(getMinimumSize());
    this.setBorder(new BorderUIResource.EtchedBorderUIResource());
    */
   this.setSize(new Dimension(161, 226));
    backButton.setFont(smallFont);
    backButton.setLabel("<");
  //  backButton.setSize(insets);
 //   backButton.setDefaultCapable(false);
    backButton.addActionListener(new ActionListener() {
      public void actionPerformed(final ActionEvent evt) {
        onBackClicked(evt);
      }
    });
    add(backButton, new AbsoluteConstraints(10, 10, 20, 20));
    monthAndYear.setFont(largeFont);
    monthAndYear.setAlignment((int)TextField.CENTER_ALIGNMENT);
    monthAndYear.setText(formatDateText(selectedDate.getTime()));
    add(monthAndYear, new AbsoluteConstraints(30, 10, 100, 20));
    forwardButton.setFont(smallFont);
    forwardButton.setLabel(">");
 //   forwardButton.setMargin(insets);
//    forwardButton.setDefaultCapable(false);
    forwardButton.addActionListener(new ActionListener() {
      public void actionPerformed(final ActionEvent evt) {
        onForwardClicked(evt);
      }
    });
    add(forwardButton, new AbsoluteConstraints(130, 10, 20, 20));
    int x = startX;
    for (int ii = 0; ii < dayHeadings.length; ii++) {
    //  dayHeadings[ii].setOpaque(true);
      dayHeadings[ii].setBackground(Color.LIGHT_GRAY);
      dayHeadings[ii].setForeground(Color.WHITE);
      dayHeadings[ii].setAlignment((int)TextField.CENTER_ALIGNMENT);
    //  dayHeadings[ii].setHorizontalAlignment(Label.CENTER);
      add(dayHeadings[ii], new AbsoluteConstraints(x, 40, 21, 21));
      x += 20;
    }
    x = startX;
    int y = startY;
    for (int ii = 0; ii < daysInMonth.length; ii++) {
      for (int jj = 0; jj < daysInMonth[ii].length; jj++) {
      //  daysInMonth[ii][jj].setOpaque(true);
        daysInMonth[ii][jj].setBackground(white);
        daysInMonth[ii][jj].setFont(smallFont);
     //   daysInMonth[ii][jj].setHorizontalAlignment(Label.CENTER);
        daysInMonth[ii][jj].setText("");
        daysInMonth[ii][jj].addMouseListener(new MouseAdapter() {
          public void mouseClicked(final MouseEvent evt) {
            onDayClicked(evt);
          }
        });
        add(daysInMonth[ii][jj], new AbsoluteConstraints(x, y, 21, 21));
        x += 20;
      }
      x = startX;
      y += 20;
    }
    initButtons(true);
    calculateCalendar();
  }

  private void initButtons(final boolean firstTime) {
    if (firstTime) {
      final Dimension buttonSize = new Dimension(68, 24);
      todayButton.setLabel("今天");
      todayButton.setSize(buttonSize);
      /*
      todayButton.setMargin(insets);
      todayButton.setMaximumSize(buttonSize);
      todayButton.setMinimumSize(buttonSize);
      todayButton.setPreferredSize(buttonSize);
      todayButton.setDefaultCapable(true);
      todayButton.setSelected(true);
      */
      todayButton.addActionListener(new ActionListener() {
        public void actionPerformed(final ActionEvent evt) {
          onToday(evt);
        }
      });
      cancelButton.setLabel("取消");
      cancelButton.setSize(buttonSize);
      /*
      cancelButton.setMargin(insets);
      cancelButton.setMaximumSize(buttonSize);
      cancelButton.setMinimumSize(buttonSize);
      cancelButton.setPreferredSize(buttonSize);
      */
      cancelButton.addActionListener(new ActionListener() {
        public void actionPerformed(final ActionEvent evt) {
          onCancel(evt);
        }
      });
    }
    else {
      this.remove(todayButton);
      this.remove(cancelButton);
    }
    if (hideOnSelect) {
      add(todayButton, new AbsoluteConstraints(25, 190, 52, -1));
      add(cancelButton, new AbsoluteConstraints(87, 190, 52, -1));
    }
    else {
      add(todayButton, new AbsoluteConstraints(55, 190, 52, -1));
    }
  }

  private void onToday(final java.awt.event.ActionEvent evt) {
    selectedDate = getToday();
    setVisible(!hideOnSelect);
    if (isVisible()) {
      monthAndYear.setText(formatDateText(selectedDate.getTime()));
      calculateCalendar();
    }
  }

  private void onCancel(final ActionEvent evt) {
    selectedDate = originalDate;
    setVisible(!hideOnSelect);
  }

  private void onForwardClicked(final java.awt.event.ActionEvent evt) {
    final int day = selectedDate.get(Calendar.DATE);
    selectedDate.set(Calendar.DATE, 1);
    selectedDate.add(Calendar.MONTH, 1);
    selectedDate.set(Calendar.DATE,
                     Math.min(day, calculateDaysInMonth(selectedDate)));
    monthAndYear.setText(formatDateText(selectedDate.getTime()));
    calculateCalendar();
  }

  private void onBackClicked(final java.awt.event.ActionEvent evt) {
    final int day = selectedDate.get(Calendar.DATE);
    selectedDate.set(Calendar.DATE, 1);
    selectedDate.add(Calendar.MONTH, -1);
    selectedDate.set(Calendar.DATE,
                     Math.min(day, calculateDaysInMonth(selectedDate)));
    monthAndYear.setText(formatDateText(selectedDate.getTime()));
    calculateCalendar();
  }

  private void onDayClicked(final java.awt.event.MouseEvent evt) {
    final Label fld = (Label) evt.getSource();
    if (!"".equals(fld.getText())) {
      fld.setBackground(highlight);
      selectedDay = fld;
      selectedDate.set(Calendar.DATE, Integer.parseInt(fld.getText()));
      setVisible(!hideOnSelect);
    }
  }

  private static GregorianCalendar getToday() {
    final GregorianCalendar gc = new GregorianCalendar();
    gc.set(Calendar.HOUR_OF_DAY, 0);
    gc.set(Calendar.MINUTE, 0);
    gc.set(Calendar.SECOND, 0);
    gc.set(Calendar.MILLISECOND, 0);
    return gc;
  }

  private void calculateCalendar() {
    if (null != selectedDay) {
      selectedDay.setBackground(white);
      selectedDay = null;
    }
    final GregorianCalendar c = new GregorianCalendar(selectedDate.get(Calendar.
        YEAR), selectedDate.get(Calendar.MONTH), 1);
    final int maxDay = calculateDaysInMonth(c);
    final int selectedDay = Math.min(maxDay, selectedDate.get(Calendar.DATE));
    int dow = c.get(Calendar.DAY_OF_WEEK);
    for (int dd = 0; dd < dow; dd++) {
      daysInMonth[0][dd].setText("");
    }
    int week;
    do {
      week = c.get(Calendar.WEEK_OF_MONTH);
      dow = c.get(Calendar.DAY_OF_WEEK);
      final Label fld = this.daysInMonth[week - 1][dow - 1];
      fld.setText(Integer.toString(c.get(Calendar.DATE)));
      if (selectedDay == c.get(Calendar.DATE)) {
        fld.setBackground(highlight);
        this.selectedDay = fld;
      }
      if (c.get(Calendar.DATE) >= maxDay)
        break;
      c.add(Calendar.DATE, 1);
    }
    while (c.get(Calendar.DATE) <= maxDay); week--;
    for (int ww = week; ww < daysInMonth.length; ww++) {
      for (int dd = dow; dd < daysInMonth[ww].length; dd++) {
        daysInMonth[ww][dd].setText("");
      }
      dow = 0;
    }
    c.set(Calendar.DATE, selectedDay);
    selectedDate = c;
  }

  private static int calculateDaysInMonth(final Calendar c) {
    int daysInMonth = 0;
    switch (c.get(Calendar.MONTH)) {
      case 0:
      case 2:
      case 4:
      case 6:
      case 7:
      case 9:
      case 11:
        daysInMonth = 31;
        break;
      case 3:
      case 5:
      case 8:
      case 10:
        daysInMonth = 30;
        break;
      case 1:
        final int year = c.get(Calendar.YEAR);
        daysInMonth = (0 == year % 1000) ? 29 : (0 == year % 100) ? 28 :
            (0 == year % 4) ? 29 : 28;
        break;
    }
    return daysInMonth;
  }

  private static String formatDateText(final Date dt) {
    final DateFormat df = DateFormat.getDateInstance(DateFormat.LONG);
    final StringBuffer mm = new StringBuffer();
    final StringBuffer yy = new StringBuffer();
    final FieldPosition mmfp = new FieldPosition(DateFormat.MONTH_FIELD);
    final FieldPosition yyfp = new FieldPosition(DateFormat.YEAR_FIELD);
    df.format(dt, mm, mmfp);
    df.format(dt, yy, yyfp);
    return (mm.toString().substring(mmfp.getBeginIndex(), mmfp.getEndIndex()) +
            "月 " +
            yy.toString().substring(yyfp.getBeginIndex(), yyfp.getEndIndex()) +
            "年");
  }
}

开发企业级的应用程序需要搭建好J2EE的运行环境。其实也就是到SUN公司的网站上去DOWN下J2EE 1.4 SDK开发工具包。然后双击安装文件，如果你下载的版本与我的一样。那么这个安装文件就会是这个名字：j2eesdk-1_4-dr-windows-eval.exe。同样的我们也将J2EE SDK安装在C盘根目录下。

需要特别提醒大家的是：J2EE运行环境的搭建是以J2SE运行环境的搭建为基础的。其实想也想得到为什么。如果没有JDK，哪里来的编译和运行命令呢（JAVA和javac）。安装完J2EE 1.4 SDK包后，具体的设置与测试步骤如下：

1、  首先右往PATH变量里添加J2EE SDK的BIN目录。如：C:\j2sdkee1.3.1\bin。如何往里面添加，前面已经讲过。

2、  然后新建两个变量：一个是JAVA_HOME，变量值为：JDK的安装目录。另一个是J2EE_HOME，变量值为J2EE SDK的安装目录。如图示：
3、  最后往CLASSPATH变量里添加一个关键的JAR包。它就是J2EE.JAR包。比如我添加的就是：C:\j2sdkee1.3.1\lib\j2ee.jar。

4、  所有的工作做完以后。大家可以通过以下方式验证一下我们的J2EE环境是否已经搭建成功。在命令提示符状态下输入命令：J2EE －Verbose。如果屏幕的最下面看到了这样一句话J2EE server startup complete.那就表示J2EE服务器成功启动了。在我们的J2EE程序要布署和运行的过程中。服务器将一直启动着。

另外提一下，如果你需要停止J2EE服务器，必须再开一个命令窗口，并运行如下命令：J2EE –STOP。成功运行后，将会有提示语句。再去看看启动服务器的那个窗口，你将可以看到提示符了。

5、  这样做了还不够，我们还需要到网页里去测试一下服务器默认页面是否能够正常显示，这样才能保证我们能够进WEB程序的开发。双击IE浏览器的图标，在地址栏里输入：http://localhost:8000,如果你能看到以下窗口中的内容，那就说明你的J2EE环境已经搭建成功。需要说明一点，在localhost:后的是J2EE服务器提供的WEB服务端口号。

需要提醒大家的是：当你打开网页之前，确认你的J2EE服务器是启动着的。如果你机器上没有安装网卡，或是网卡安装不正确，也会导致无法打开J2EE服务器默认页面。

常用的ant的操作

常用的ant的操作，方便自己查询，所以传到网上，如果有朋友觉得不够，请补充：
主要的内容有：
  (1)建立一个项目
  (2)建立属性
  (3)对数据库的操作
  (4)javac编译
  (5)删除目录
  (6)建立目录
  (7)拷贝文件群
  (8)jar为一个包
  (9)拷贝单个文件
  (10)运行
有更多更好的常用的,我没想到的,希望大家补充。  
  
<!--(1)建立一个项目，默认的操作为target=all. -->
<project name="proj" default="all" basedir=".">

  <!--(2)建立一些属性，以供下边的操作用到 -->
  <property name="root"  value="./" />
  <property name="deploy_path"  value="d:/deploy" />
  <property name="srcfile"  value="d:/srcfile" /> 
 
  <target name="all" depends="compile,deploy"/>
 
  <!--(3)对数据库的操作 demo.ddl中写的是sql语句 driver,url,userid,password随具体情况设置--> 
  <!-- Oracle -->
  <target name="db_setup_oracle" description="Database setup for Oracle">
    <antcall target="check_params_results"/>
    <sql driver="oracle.jdbc.driver.OracleDriver"
       url="jdbc:oracle:thin:@192.168.0.1:1521:oa"
       userid="oa" password="oa"
       onerror="continue"
       print="yes"
       src="./demo.ddl"/>
  </target>

  <!--(4)javac编译 --> 
  <target name="compile">  
    <javac srcdir="${srcfile}"
      destdir="${root}/oa/"
      includes="*.java"
      classpath="${CLASSPATH};${CLIENT_CLASSES}/utils_common.jar"   <!--CLASSPATH和CLIENT_CLASSES是环境变量-->
    />
  </target>
 
  <target name="deploy" depends="compile">
    <!-- Create the time stamp -->
    <tstamp/>
   
    <!--(5)删除目录-->   
    <!--(6)建立目录-->
    <delete dir="${root}/dist/"/>   
    <mkdir dir="${root}/dist/"/>      

    <delete dir="${deploy_path}"/>   
    <mkdir dir="${deploy_path}"/>    
 
    <!--(7)拷贝文件群-->
    <copy todir="${root}/dist/">    
            <fileset dir="${root}/oa/">
                <include name="*.class"/>
            </fileset>
    </copy&g

ps:from Thinking in Java chapter 4

Consider a class called Dog:

1. The first time an object of type Dog is created (the constructor is actually a static method), or the first time a static method or static field of class Dog is accessed, the Java interpreter must locate Dog.class, which it does by searching through the classpath. 
2. As Dog.class is loaded (creating a Class object, which you’ll learn about later), all of its static initializers are run. Thus, static initialization takes place only once, as the Class object is loaded for the first time. 
3. When you create a new Dog( ), the construction process for a Dog object first allocates enough storage for a Dog object on the heap. 
4. This storage is wiped to zero, automatically setting all the primitives in that Dog object to their default values (zero for numbers and the equivalent for boolean and char) and the references to null. 
5. Any initializations that occur at the point of field definition are executed. 
6. Constructors are executed. As you shall see in Chapter 6, this might actually involve a fair amount of activity, especially when inheritance is involved.