JavaIO and Applet

8/22/2019 JavaIO and Applet

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1Information Science and Engineering


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Stream

A stream is an abstraction that either produces or consumes

information.

* Byte Stream* Character Stream

BufferedInputStream

BufferedOutputStream

ByteArrayInputStream

ByteArrayOutputStreamFilterOutputStream

FilterInputStream

PrintStream

InputStream

DataInputStream

RandomAccessFileDataOutputStream

SequenceInputStream

BufferedReader

BufferedWriter

InputStreamReader

CharArrayWriterCharArrayReader

LineNumberReader

FileWriter

Reader

File

FileDescriptorFileInputStream

PrintWriter

FilterWriter

FilterReader

FileOutputStream


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Reading Console Input

console input is accomplished by reading from System.in

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

BufferedReader :

BufferedReader(Reader inputReader)

int read( ) throws IOException

String readLine( ) throws IOException


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import java.io.*;

class BRRead {

public static void main(String args[]) throws IOException

{char c;


System.out.println("Enter characters, 'q or Q' to quit.");

// read characters

do {

c = (char) br.read();System.out.println(c);

} while(c != 'q' || c !=Q );

}

}


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import java.io.*;

class BRReadLines

{public static void main(String args[]) throws IOException

{

// create a BufferedReader using System.in


String str;

System.out.println("Enter lines of text.");str = br.readLine();

System.out.println(str);

}

}

void write(int byteval) throws IOException


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PrintWriter Class

PrintWriter(OutputStream outputStream, boolean flushOnNewline)

PrintWriter pw = new PrintWriter(System.out, true);

import java.io.*;

public class PrintWriterDemo

{public static void main(String args[])

{

PrintWriter pw = new PrintWriter(System.out, true);

pw.println("This is a string");

int i = -7;

pw.println(i);

double d = 4.5e-7;

pw.println(d);

}

}


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java.lang

Integer

CharacterFloat

Double

Short

Byte

Boolean etc.,

class DoubleDemo

{

public static void main(String args[])

{

Double d1 = new Double(3.14159);Double d2 = new Double("314159E-5");

System.out.println(d1 + " = " + d2 + " -> " + d1.equals(d2));

}

}


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static short parseShort(String str) throws NumberFormatException

static int parseInteger(String str) throws NumberFormatException

static int parseInt(String str, int radix) throws NumberFormatException

static long parseLong(String str) throws NumberFormatException


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import java.io.*;

class ParseDemo

{

public static void main(String args[]) throws IOException

{BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

String str;

int I;

try {

System.out.println(Enter a number : );

str = br.readLine();

i = Integer.parseInt(str);

}

catch(NumberFormatException e)

{

System.out.println("Invalid format");

}

System.out.println(Given number is : + i);

}

}Integer.toBinaryString(num)


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Reading and Writing Files

FileInputStream(String fileName) throws FileNotFoundException

FileOutputStream(String fileName) throws FileNotFoundException

void close( ) throws IOException

int read( ) throws IOException

void write(int byteval) throws IOException


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import java.io.*;

class ShowFile {


throws IOException

{int i;

FileInputStream fin;

try {

fin = new FileInputStream(abc.txt);

}

catch(FileNotFoundException e){

System.out.println("File Not Found");

return;

}

do

{i = fin.read();

if(i != -1) System.out.print((char) i);

} while(i != -1);

fin.close();

}

}


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try {

fout = new FileOutputStream(args[1]);

}

catch(FileNotFoundException e){

System.out.println("Error Opening Output File");

return;

}

fout.write(i);


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File

A File object is used to obtain or manipulate the information associated with a

disk file, such as the permissions, time, date, and directory path, and tonavigate subdirectory hierarchies.

File(String directoryPath)

File(String directoryPath, String filename)

File(File dirObj, String filename)

File(URI uriObj)

Example:

File f1 = new File("/");

File f2 = new File("/","autoexec.bat");

File f3 = new File(f1,"autoexec.bat");


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import java.io.File;

class FileDemo

{

static void p(String s) { System.out.println(s); }


{

File f1 = new File("/java/COPYRIGHT");

p("File Name: " + f1.getName());

p("Path: " + f1.getPath());p("Abs Path: " + f1.getAbsolutePath());

p("Parent: " + f1.getParent());

p(f1.exists() ? "exists" : "does not exist");

p(f1.canWrite() ? "is writeable" : "is not writeable");

p(f1.canRead() ? "is readable" : "is not readable");

p("is " + (f1.isDirectory() ? "" : "not" + " a directory"));p(f1.isFile() ? "is normal file" : "might be a named pipe");

p(f1.isAbsolute() ? "is absolute" : "is not absolute");

p("File last modified: " + f1.lastModified());

p("File size: " + f1.length() + " Bytes");

}

}


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boolean renameTo(File newName);

boolean delete( );

void deleteOnExit( )

boolean isHidden( )

Removes the file associated with the

invoking object when the Java Virtual

Machine terminates.

Returns true if the invoking file is

hidden. Returns false otherwise.

boolean setLastModified(long millisec)

boolean setReadOnly( )

Sets the time stamp on the invoking

file to that specified by millisec, whichis the number of milliseconds from

January 1, 1970, Coordinated

Universal Time (UTC).

Sets the invoking file to read-only.


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import java.io.File;

class DirList

{


{ String dirname = "/java";

File f1 = new File(dirname);

if (f1.isDirectory())

{

System.out.println("Directory of " + dirname);

String s[] = f1.list();for (int i=0; i < s.length; i++)

{

File f = new File(dirname + "/" + s[i]);

if (f.isDirectory()) {

System.out.println(s[i] + " is a directory");

}else {

System.out.println(s[i] + " is a file");

}

} else { System.out.println(dirname + " is not a directory"); }

}

}


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Using FilenameFilter

String[ ] list(FilenameFilterFFObj)

boolean accept(File directory, String filename)

import java.io.*;

public class OnlyExt implements FilenameFilter

{

String ext;

public OnlyExt(String ext)

{

this.ext = "." + ext;

}

public boolean accept(File dir, String name)

{

return name.endsWith(ext);

}

}


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import java.io.*;

class DirListOnly

{

public static void main(String args[]){

String dirname = "/java";

File f1 = new File(dirname);

FilenameFilter only = new OnlyExt("html");

String s[] = f1.list(only);

for (int i=0; i < s.length; i++){

System.out.println(s[i]);

}

}

}


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An applet is a Java program that runs on aweb page

Applets can be run from:

Internet ExplorerNetscape Navigator (sometimes)

appletviewer

An application is a Java program that runs all

by itself


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The Applet class

To create an applet, you must import theApplet class

This class is in the java.applet package

The Applet class contains code that workswith a browser to create a display window

Capitalization matters!

applet and Applet are different names

import java.applet.Applet;


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The java.awtpackage includes classes for:

Drawing lines and shapes

Drawing letters

Setting colorsChoosing fonts

paintneeds to be told where on the screen it can draw

public void paint(Graphics g)

AWT methods :

g.drawString(String", int x, int y);

g.setColor(Color.RED);

g.drawRect( left, top , width , height);

g.fillRect(left, top , width , height);etc


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import java.awt.*;

import java.applet.*;

public class SimpleApplet extends Applet

{ public void paint(Graphics g)

{

g.drawString(Hello World! ", 20, 20);

}

}

public void init ()

public void start ()

public void stop ()

public void destroy ()public void paint (Graphics)

Also:

public void repaint()

public void update (Graphics)

public void showStatus(String)

public String getParameter(String)

Applet methods :


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init()

start()

stop()

destroy()

do some work


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How to RUN :


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import java.applet.Applet;

import java.awt.Graphics;

import java.awt.Color;public class SimpleApplet extends Applet

{

String text = "I'm a simple applet";

public void init()

{

text = "I'm a simple applet";setBackground(Color.cyan);

}

public void start()

{

System.out.println("starting...");

}public void stop()

{

System.out.println("stopping...");

}

public void destroy(){

System.out.println("preparing to unload...");

}


{

System.out.println("Paint");g.setColor(Color.blue);

g.drawRect(0, 0, getSize().width -1,

getSize().height -1);

g.setColor(Color.red);

g.drawString(text, 15, 25);

}}


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Sample Graphics methods

g.drawRect(x, y, width, height);g.fillRect(x, y, width, height);

g.drawOval(x, y, width, height);

g.fillOval(x, y, width, height);

g.setColor(Color.red);

g.drawString(Hello, 20, 20); Hello


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Color.black Color.magenta

Color.blue Color.orangeColor.cyan Color.pink

Color.darkGray Color.red

Color.gray Color.white

Color.green Color.yellow

Color.lightGray

setBackground(Color.cyan);

setForeground(Color.red);


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// Using the Status Window.

import java.awt.*;


/*

*/

public class StatusWindow extends Applet

{

public void init(){


}

// Display msg in applet window.


{g.drawString("This is in the applet window.", 10, 20);

showStatus("This is shown in the status window.");

}

}


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import java.awt.*;


public class SimpleBanner extends Applet implements Runnable

{String msg = " A Simple Moving Banner.";

Thread t = null;

int state;

boolean stopFlag;

// Set colors and initialize thread.

public void init() {


setForeground(Color.red);

}

// Start threadpublic void start() {

t = new Thread(this);

stopFlag = false;

t.start();

}

public void run() {


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public void run() {

char ch;

for( ; ; ) {

try {

repaint();

Thread.sleep(250);ch = msg.charAt(0);

msg = msg.substring(1, msg.length());

msg += ch;

if(stopFlag)

break;

} catch(InterruptedException e) { }}

}

public void stop() {

stopFlag = true;

t = null;

}// Display the banner.

public void paint(Graphics g) {

g.drawString(msg, 50, 30);

}

}


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The HTML APPLET Tag

< APPLET

[CODEBASE = codebaseURL]CODE = appletFile

[ALT = alternateText]

[NAME = appletInstanceName]

WIDTH =pixels HEIGHT = pixels

[ALIGN = alignment]

[VSPACE =pixels] [HSPACE = pixels]>

[< PARAM NAME =AttributeName VALUE = AttributeValue>]

[< PARAM NAME =AttributeName2 VALUE = AttributeValue>]

. . .

[HTML Displayed in the absence of Java]


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// Applet program to Use Parameters

import java.awt.*;


public class ParamDemo extends Applet

{

String SName;

int Sage;

boolean active;// Initialize the string to be displayed.

public void start()

{

String param;


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SName = getParameter(StuName");

if(SName == null)

SName = "Not Found";

param = getParameter(age");

try {if(param != null) // if not found

Sage = Integer.parseInt(param);

else

Sage = 0;

} catch(NumberFormatException e) {

Sage = 0;}

}


{

g.drawString(Student name : " + SName, 0, 10);

g.drawString(Student age : " + Sage, 0, 26);}

}


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getDocumentBase( ) and getCodeBase( )

import java.awt.*;


import java.net.*;

public class Bases extends Applet

{


{

String msg;

URL url = getCodeBase(); // get code base

msg = "Code base: " + url.toString();

g.drawString(msg, 10, 20);

url = getDocumentBase(); // get document base

msg = "Document base: " + url.toString();g.drawString(msg, 10, 40);

}

}


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AppletContext and showDocument( )

showDocument( ) method defined by the AppletContext interface

import java.awt.*;


import java.net.*;

public class ACDemo extends Applet

{

public void start()

{

AppletContext ac = getAppletContext();

URL url = getCodeBase(); // get url of this applet

try {

ac.showDocument(new URL(url+"Test.html"));

} catch(MalformedURLException e) {showStatus("URL not found");

}

}

}


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JSP JAVA Server Pages

JSP Tags


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Your Age is :

Your name is :

Your Age is :


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Methods :

Your value is :


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10) { %>

X value is greater then 10

X value is less then 10

Use of if statement


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JDBCClass driver_class=null;

try {driver_class = Class.forName("com.mysql.jdbc.Driver");

} catch (ClassNotFoundException e) {

e.printStackTrace();

}

System.out.println("Found driver " + driver_class);

Connection connection=null;

try {

connection = DriverManager.getConnection

("jdbc:mysql://localhost:3306/ecs160tutorial","tutorialuser","123456");} catch (SQLException e) {

e.printStackTrace();

}


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Statement statement = connection.createStatement();

statement.execute("SELECT * FROM simple_table");

ResultSet resset = statement.getResultSet();

System.out.println("Row Name Last_Name");while(resset.next())

{

System.out.print(resset.getRow());

System.out.print(" " + resset.getString("name"));

System.out.println(" " + resset.getString("last_name"));

}resset.close();


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import java.sql.*


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JavaIO and Applet