Java Programming - 06 java file io

Module 06 – Java File IO
Danairat T.
Line ID: Danairat
FB: Danairat Thanabodithammachari
+668-1559-1446

Fundamental Java Programming
The Course Outline
Module 01 – Introduction to Java
Module 02 – Basic Java Programming
Module 03 – Control Flow and Exception Handling
Module 04 – Object Oriented in Java
Module 05 – Java Package and Access Control
Module 07 – Java Networking
Module 08 – Java Threading

• IO Stream
• Byte Stream
• Character Stream
• Listing Directory Objects (Directory and File)
• Creating Directory and File
• Deleting Directory and File
• Java Console Stream

I/O Streams
An I/O Stream represents an input source or an output destination. A
stream can represent many different kinds of sources and destinations,
including disk files, devices, other programs, and memory arrays.
Input Stream Output Stream

Byte Streams
The low level File IO process is using Byte Stremes; FileInputStream and FileOutputStream
package com.mycompany.fileio;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class CopyBytes {
public static void main(String[] args) throws IOException {
FileInputStream in = null;
FileOutputStream out = null;
try {
in = new FileInputStream("inputfile.txt");
out = new FileOutputStream("outagain.txt");
int c;
while ((c = in.read()) != -1) {
out.write(c); System.out.println(c);
}
} finally {
if (in != null) {
in.close();
}
if (out != null) {
out.close();
}
}
}
}

Character Stream with Line Reader
package com.mycompany.fileio;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.util.StringTokenizer;
public class CopyLinesBuffered {
public static void main(String[] args) throws IOException {
BufferedReader inputStream = null;
BufferedWriter outputStream = null;
try {
inputStream =
new BufferedReader(new FileReader("inputfile.txt"));
outputStream =
new BufferedWriter(new FileWriter("lineoutput.txt"));
String l;
while ((l = inputStream.readLine()) != null) {
outputStream.write(l);
System.out.println("line data->"+l);
StringTokenizer st = new StringTokenizer(l," ");
while (st.hasMoreTokens()) {
System.out.println(st.nextToken()+"|");
}
}
} finally {
if (inputStream != null) {
inputStream.close();
}
if (outputStream != null) {
outputStream.close();
}
}
}
}

Listing Directory Objects
import java.io.File;
public class ListDirectoryObjects {
public static void main(String[] a) {
File myFile = new File("C:" + File.separator);
// reture String
for (String s : myFile.list()) {
System.out.println(s);
}
// return File obj for next iterative
for(File s: myFile.listFiles()){
System.out.println(s);
}
}
}

Creating Directory and File
public class FileDemo {
public static void main(String[] a)throws Exception {
File file = new File("d:JavaDemoJavaDemoSub");
file.mkdirs();
file = new File("d:JavaDemoJavaDemoSubtest.txt");
file.createNewFile();
}
}

Deleting Directory and File
public class DeleteFile_Dir_Demo {
public static void main(String args[]) {
File f = new File("D:" + File.separator + "temp4" + File.separator + "a.txt");
if (f.exists()) {
f.delete();
}
}
}

Delete File Recurrsively
public class DeleteDirectoryTree {
public static void main(String args[]) {
deleteDirectory(new File("v:delete_tempdelete_demo"));
}
static public boolean deleteDirectory(File path) {
if( path.exists() ) {
File[] files = path.listFiles();
for(int i=0; i<files.length; i++) {
if(files[i].isDirectory()) {
deleteDirectory(files[i]);
}
else {
files[i].delete();
}
}
}
return( path.delete() );
}
}

Java Console
Start from Java SE6, It is a predefined object of type Console that has most of
the features provided by the Standard Console Streams.
import java.io.Console;
import java.util.Arrays;
public class ConsolePassword {
public static void main (String args[]) throws IOException {
Console c = System.console();
if (c == null) {
System.err.println("No console.");
System.exit(1);
}
String login = c.readLine("Enter your login: ");
char [] oldPassword = c.readPassword("Enter your old
password: ");
if (verify(login, oldPassword)) {
boolean noMatch;
do {
char [] newPassword1 =
c.readPassword("Enter your new password: ");
char [] newPassword2 =
c.readPassword("Enter new password again: ");
noMatch = ! Arrays.equals(newPassword1,
newPassword2);
if (noMatch) {
c.format("Passwords don't match. Try
again.");
} else {
change(login, newPassword1);
c.format("Password changed.", login);
}
Arrays.fill(newPassword1, ' '); // clear data
Arrays.fill(newPassword2, ' '); // clear data
} while (noMatch);
}
Arrays.fill(oldPassword, ' '); // clear data
}
//Dummy verify method.
static boolean verify(String login, char[] password) {
return true;
}
//Dummy change method.
static void change(String login, char[] password) {}
}

Java Console – Deploy and Test
1.) Select “New ” from project menu 2.) Select “Deployment Profiles” -> “JAR File”

3.) Enter Application Name
“console_password_app”
4.) Click “Browse” to select the start class file

5.) Select the starting class “ConsolePassword” 6.) Click “Filters”

7.) Check only the required class.
“ConsolePassword.java”
8.) Click “OK”

9.) Click “Deploy” and select “console_password_app” 10.) Click “Next”

11.) Click “Finish” 12.) Execute application from command line mode.
java –jar console_password_app.jar

Danairat T.
Line ID: Danairat
FB: Danairat Thanabodithammachari
+668-1559-1446
Thank you

Java Programming - 06 java file io

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