Úvod do programovacích jazyku˚ (java) · package chess; import java.lang.*; import...

Úvod do programovacíchjazyku (Java)

Michal Kratky

michal.kratky@vsb.cz

Katedra informatiky

http://www.cs.vsb.cz/kratky

Uvod do programovacch jazyku (Java) – p. 1/82

Zápocet a zkouška

Zápocet >= 21b (ze 40 možných). Dvasemestrální projekty.

Predmet ukoncen klasifikovaným zápoctem.Min. 30b z 60 možných.

JDK a vývojováprostredí

http://java.sun.com – JDK – JavaPlatforma, aktuální verze 1.5

http://www.eclipse.org – Eclipse,vývojové prostredí

http://jikes.sourceforge.net/ –rychlý prekladac

Literatura

B. Eckel: Thinking in Java. 2002,http://www.mindview.net/Books/TIJ

Sun MicroSystems: Sun Developer Network.2005, http://java.sun.com

R. Szturc: Introduction to Programming(Java). Department of Computer Science,VŠB – Technical University of Ostrava, 2004,http://www.cs.vsb.cz/java/index.html

Example 1

public class Example1

public static void main(String[] args)

int i = 5;

int j = i + 3;

System.out.println("i=" + i + ", j=" +

j + "\n");

i=5, j=8Uvod do programovacch jazyku (Java) – p. 5/82

Example 2

int i = 6, j = 3;

int div = i / j;

int mod = i % j;

System.out.println("div = " + div +

", mod = " + mod + "\n");

div = 2, mod = 0Uvod do programovacch jazyku (Java) – p. 6/82

Example 3

int i = 6;

System.out.println("i = " + (-i));

System.out.println("i = " + (++i));

System.out.println("i = " + (i++));

System.out.println("i = " + i);

i = -6 i = 7 i = 7 i = 8Uvod do programovacch jazyku (Java) – p. 7/82

Example 4

float a = (float)9.0;

if (a / 3 == 3.0)

System.out.println("ok");

}Uvod do programovacch jazyku (Java) – p. 8/82

Example 5

int value = 1 << 2;

System.out.println(value);

00000001 << 2 = 00000100

Complement –negative numbers

-1, 1 = 00000001

˜00000001 = 11111110 + 1 = 11111111 = 255

-1 >> 2 = -1

-1 << 2 = -4 (11111011 + 1 = 11111100)

-1 >>> 30 = 3

Example 6

public class Example6 {

boolean val = true;

double res = 0.0;

res1 = (val == true) ? 1.0 : 3.0;

res2 = (val) ? 1.0 : 3.0;

System.out.println(res1 + "," + res2);

1.0, 1.0

Example 7

double val = 3.14;

int res = (int)val;

System.out.println(res);

Example 7.5

public class Example7DOT5

int res = 0, a = 2, b = 1;

if ((res = a + b) > 2)

System.out.print("ok");

Example 8

int i = 0;

for ( ; i < 8 ; i++)

int val = 1 << i;

System.out.println(val);

1 2 4 8 16 32 64 128 ... Uvod do programovacch jazyku (Java) – p. 14/82

Example 9

public class Example9 {

public static void main(String[] args) {

int val = 1;

int i = 0;

while (val > 0)

System.out.print(val + ", ");

val <<= 1;

1, 2, 4, 8, 16, 32, 64, ... , 1073741824

Example Triangle1/11

import java.math.*;

public class Coordinate {

public static int DEFAULT_DIMENSION = 2;

private int mDimension;

private double mValues[];

public Coordinate(int dimension) {

mDimension = dimension;

mValues = new double[mDimension];

public void SetValue(int order, double value){

if (order >= 0 && order < mDimension) {

mValues[order] = value;

public double GetValue(int order) {

if (order >= 0 && order < mDimension) {

return mValues[order];

else {

return -1.0;

public int GetDimension()

return mDimension;

public void Print()

for (int i = 0 ; i < mDimension ; i++)

System.out.print(mValues[i] + ",");

System.out.println(" ");

public static double Distance(Coordinate c1,

Coordinate c2) {

double distance = 0.0;

for (int i=0 ; i < c1.GetDimension() ; i++)

double diff=c2.GetValue(i)-c1.GetValue(i);

distance += diff * diff;

return Math.sqrt(distance);

public class Triangle {

public static final int VERTEXES_NUMBER = 3;

private Coordinate mVertexes[];

public Triangle() {

int dimension = 2;

mVertexes = new Coordinate[VERTEXES_NUMBER];

for (int i = 0 ; i < VERTEXES_NUMBER ; i++)

mVertexes[i] = new Coordinate(dimension);

public Coordinate GetVertex(int order)

if (order >=0 && order < VERTEXES_NUMBER)

return mVertexes[order];

return null;

public double Perimeter()

return

Coordinate.Distance(mVertexes[0],

mVertexes[1]) +

mVertexes[2]) +

mVertexes[0]);

import java.io.*;

public class TriangleRun {

private Triangle mTriangle;

public static void main(String args[])

new TriangleRun().Run();

public TriangleRun()

mTriangle = new Triangle();

public int Run()

byte array[] = new byte[1024];

for (int i=0 ; i < Triangle.VERTEXES_NUMBER ;

for (int j=0 ; j<mTriangle.GetVertex(i)

.GetDimension() ; j++) {

System.in.read(array);

String str = new String(array);

double value = Double.parseDouble(str);

mTriangle.GetVertex(i).SetValue(j, value);

} catch (IOException ioe) {

System.out.println( "IO error:" + ioe );

Example Triangle11/11mTriangle.GetVertex(i).Print();

System.out.println("perimeter: " +

mTriangle.Perimeter());

return 0;

Chess – Files1/5

<chess>

<model>

<view>

Board.java

ChessRun.java

Chess – Compilation& Run – 2/5

d:\projs> javac chess\ChessRun.java

d:\projs>set PATH=%PATH%;d:\...\jdk1.5.0_03\bin

d:\projs>set CLASSPATH=%CLASSPATH%;.

d:\projs> java chess.ChessRun

Chess – ChessRun3/5

* Class of the chess game

* @author Michal Kratky

* @created 7.11.2005

package chess;

public class ChessRun {

public static void main(String args[]) {

new Board().Run();

Chess – Board I4/5

package chess;

import java.lang.*;

import chess.model.*;

public class Board

public static int FIELD_NUMBER = 8;

private ChessPiece mGameArray[][];

Chess – Board II4/5

* Board class constructor

* @param value Description of the Parameter

public Board()

mGameArray =

new ChessPiece[FIELD_NUMBER][FIELD_NUMBER];

Chess – ChessPiece5/5

* ChessPiece - parent of the all chess pieces

* @author Michal Kratky

* @created 7.11.2005

package chess.model;

abstract public class ChessPiece

...Uvod do programovacch jazyku (Java) – p. 32/82

Chess – jar file – 6/d:\projs> jar cvfm mymanifest chess.jar chess/*

file: mymanifest

Main-Class: chess.ChessRun

d:\projs>java -jar chess.jar

GUI Example -Waterwolf 1/11

WWW browser, HTTP client

Waterwolf 2/11/**

* Author: Michal Kratky

* Project: WaterwolfForm

* File: WaterwolfForm.java

* Data: 11.12.2005

import javax.swing.*;

import java.awt.*;

import java.awt.event.*;

import java.net.*;

import java.io.*;Uvod do programovacch jazyku (Java) – p. 35/82

Waterwolf 3/11public class WaterwolfForm extends JFrame

implements ActionListener

public final static int BUFFER_LENGTH =1024;

public final static int TEXT_AREA_ROWS = 20;

public final static int TEXT_AREA_COLUMNS=100;

JTextField mTfUrl = new JTextField("");

JButton mBtnGo = new JButton("Go!");

JTextArea mTextArea = new JTextArea("",

TEXT_AREA_ROWS, TEXT_AREA_COLUMNS);

Waterwolf 4/11public WaterwolfForm(String strUrl)

JLabel lblUrl = new JLabel("URL:");

JPanel northPanel = new JPanel(

new BorderLayout());

mTfUrl.setText(strUrl);

northPanel.add(BorderLayout.WEST, lblUrl);

northPanel.add(BorderLayout.CENTER, mTfUrl);

northPanel.add(BorderLayout.EAST, mBtnGo);

Waterwolf 5/11JPanel mainPanel = new JPanel();

mainPanel.add(BorderLayout.NORTH,

northPanel);

JScrollPane scrollPane = new JScrollPane(

mTextArea);

getContentPane().add(BorderLayout.NORTH,

northPanel);

getContentPane().add(BorderLayout.CENTER,

scrollPane);

Waterwolf 6/11// set gui

pack();

setTitle("Waterwolf 0.0001");

// add listeners

mBtnGo.addActionListener(this);

Waterwolf 7/11/** Button events. */

public void actionPerformed(ActionEvent e)

System.out.println(mTfUrl.getText());

StringBuffer line = new StringBuffer(

BUFFER_LENGTH);

URL url = new URL(mTfUrl.getText());

InputStream in = url.openStream();

BufferedInputStream bufIn =

new BufferedInputStream(in);Uvod do programovacch jazyku (Java) – p. 40/82

Waterwolf 8/11// Repeat until end of file

int ch;

while ((ch = bufIn.read()) != -1)

line.append((char)ch);

if (ch == ’\n’) {

System.out.print(line);

mTextArea.append(line.toString());

line.delete(0, line.length());

Waterwolf 9/11catch (MalformedURLException mue)

JOptionPane.showMessageDialog(this,

"Invalid URL", "Error",

JOptionPane.ERROR_MESSAGE);

catch (IOException ioe)

JOptionPane.showMessageDialog(this, ioe,

"I/O Error", JOptionPane.ERROR_MESSAGE);

Waterwolf 10/11/** Run Waterwolf. */

public static void main(String []args)

String strUrl = "";

if (args.length == 1)

strUrl = args[0];

new WaterwolfForm(strUrl).setVisible(true);

Waterwolf 11/11

java WaterwolfForm

"http://www.cs.vsb.cz:80/kratky"

Applet Example -ChessApplet 1/10

ChessApplet 2/10/**

* Author: Michal Kratky

* Project: ChessApplet

* File: ChessApplet.java

* Data: 11.12.2005

import javax.swing.*;

import java.applet.*;

import java.awt.*;

ChessApplet 3/10public class ChessApplet extends JApplet

implements MouseListener

public static final int GAME_FIELD_POSX = 0;

public static final int GAME_FIELD_POSY = 32;

public static final int GAME_FIELD_SIZE = 32;

JLabel mLblLocation = new JLabel("");

Image mMainImage;

ChessApplet 4/10public void init() {

JPanel panel = new JPanel();

panel.add(BorderLayout.WEST,

new JLabel("Location:"));

panel.add(BorderLayout.EAST, mLblLocation);

mMainImage = createImage(400, 400);

drawGameField();

panel);

addMouseListener(this);

ChessApplet 5/10public void paint(Graphics g) {

g.drawImage(mMainImage, GAME_FIELD_POSX+0,

GAME_FIELD_POSY+0, this);

public void update(Graphics g) {

paint(g);

public void mouseClicked(MouseEvent e) {

mLblLocation.setText(e.getPoint().getX() +

", " + e.getPoint().getY());

repaint();

ChessApplet 6/10public void mouseExited(MouseEvent e)

public void mouseEntered(MouseEvent e)

public void mouseReleased(MouseEvent e)

public void mousePressed(MouseEvent e)

ChessApplet 7/10/**

* Draw chess game field.

public void drawGameField() {

Graphics g = mMainImage.getGraphics();

g.setColor(Color.BLACK);

g.drawRect(0, 0, 8*GAME_FIELD_SIZE,

8*GAME_FIELD_SIZE);

int posx = 0;

int posy = 0;

boolean oddFlag = true;Uvod do programovacch jazyku (Java) – p. 51/82

ChessApplet 8/10for (int i = 0 ; i < 8 ; i++) {

if (!oddFlag)

posx = 0;

posx = GAME_FIELD_SIZE;

for (int j = 0 ; j < 4 ; j++) {

g.fillRect(posx, posy, GAME_FIELD_SIZE,

GAME_FIELD_SIZE);

posx += 2*GAME_FIELD_SIZE;

posy += GAME_FIELD_SIZE;

oddFlag = !oddFlag;

}}}Uvod do programovacch jazyku (Java) – p. 52/82

ChessApplet 9/10chessapplet.html

<html>

<body>

<applet code="ChessApplet.class"

width="400" height="400"/>

</body>

</html>

ChessApplet 10/10

Model/View Example- Counter 1/12

Counter 2/12

public interface CounterType

public void increment();

public void decrement();

Counter 3/12import java.util.*;

public class Counter extends Observable

implements CounterType

private int mValue = 0;

public Counter(Observer o)

addObserver(o);

Counter 4/12public void setValue(int value)

this.mValue = value;

setChanged();

notifyObservers(new Integer(mValue));

public int getValue()

return mValue;

Counter 5/12public void increment()

setValue(getValue() + 1);

public void decrement()

setValue(getValue() - 1);

Counter 6/12import javax.swing.*;

import java.awt.*;

import java.util.*;

public class CounterGUI extends JFrame

implements Observer, ActionListener

protected JButton mBtnInc =

new JButton("Increment");

Counter 7/12protected JButton mBtnDec =

new JButton("Decrement");

protected JLabel mLblLabel =

new JLabel("Counter Value");

protected JTextField mTfValue =

new JTextField("0");

protected CounterType mCounter =

new Counter(this);

Counter 8/12public CounterGUI()

setLayout(new BorderLayout(15,15));

setTitle("Counter");

JPanel north = new JPanel();

north.setLayout(new BorderLayout());

north.add(BorderLayout.NORTH, mLblLabel);

north.add(BorderLayout.SOUTH, mTfValue);

Counter 9/12JPanel south = new JPanel();

south.setLayout(new GridLayout(1,2,15,15));

south.add(mBtnInc);

south.add(mBtnDec);

north);

getContentPane().add(BorderLayout.SOUTH,

south);

pack();

mBtnInc.addActionListener(this);

mBtnDec.addActionListener(this);

Counter 10/12public void actionPerformed(ActionEvent e)

if (e.getSource() == mBtnInc)

mCounter.increment();

else if (e.getSource() == mBtnDec)

mCounter.decrement();

Counter 11/12public void update(Observable c, Object arg)

mTfValue.setText(arg.toString());

new CounterGUI().setVisible(true);

Example 12/12

Counter - AdaptermBtnInc.addActionListener(new ActionListener() {

mCounter.increment();

mBtnDec.addActionListener(new ActionListener() {

mCounter.decrement();

});Uvod do programovacch jazyku (Java) – p. 67/82

Programování vláken1/12 – Motivace

Programování vláken2/12 – Úvod

Vlákno (thread) reprezentuje samostatnouposloupnost príkazu provádených voperacním systému.

Vlákno x proces. Vlákno je odlehcenýmprocesem.

Stav vlákna (Thread.State): nové (new),bežící (runnable), ukoncené (terminated), . . . .

V operacním systému je možné nastavitprioritu vlákna.

Programování vláken3/12

Pro implementaci vlákna využijeme trídujava.lang.Thread.

Možnosti:Trída dedí ze trídy Thread.Trída implementuje rozhraníjava.lang.Runnable.

public class ComputeThread extends Thread

String mId;

double mParameter;

public ComputeThread(String id, double prm)

mId = id;

mParameter = prm;

public void run()

System.out.println("Thread " + mId + " run");

double value = 2.34;

for (int i = 1 ; i < Integer.MAX_VALUE ; i++)

value += (double)i * mParameter;

System.out.println("Thread: " + mId +

", Value: " + value);

new ComputeThread("1", 1.1).start();

Pri sekvencním spouštenívýpoctu (4 x DualCoreOpteron 1.8GHz): 45s.Pri využití vláken: 15s.Notebook Intel Pentium M1.7GHz: 200s.

public class ComputeRunnable

implements Runnable

public void run()

ComputeRunnable cr1 =

new ComputeRunnable("1", 1.1);

new Thread(cr1).start();

// new ComputeThread("1", 1.1).start();

Programování vláken10/12 – Trída Thread

Thread.sleep() – uspání vlákna.

wait(), notify(), notifyAll() – metody prosynchronizaci vláken.

setPriority(int priority):Thread. MIN_PRIORITY <= priority <=Thread. MAX_PRIORITY.

Programování vláken11 – Synchronizace

Java jako vícevláknový systém se musí starato zabránení modifikace stejného objektu vícevlákny najednou.

Kód (blok nebo metoda), který nesmí býtprováden najednou se nazývá kritická sekce.

Príkaz synchronized oznacuje kritickousekci.

Objekt je uzamknut dokud je provádenakritická sekce.

Programování vláken12 – Synchronizace

public class DataStorage

private int contents;

private boolean available = false;

public synchronized int get(int who)

// DataStorage locked

// DataStorage unlocked

Generické datovétypy

List intList = new LinkedList();

intList.add(new Integer(34));

Integer x = (Integer) intList.iterator()

.next();

int value = x.intValue();

Porovnej s

List<Integer> intList =

new LinkedList<Integer>();

intList.add(new Integer(34));

Integer x = intList.iterator().next();

int value = x.intValue();

Generické datovétypy – Definice

public interface List<E>

void add(E x);

Iterator<E> iterator();

public interface Iterator<E>

E next();

boolean hasNext();

Další Javatechnologie

Datová vrstva: JDBC.

XML technologie: SAX a DOM.

Webové aplikace: Servlet, JSP.

Distribuované aplikace: RMI, CORBA.

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