Bài giảng lập trình hướng đối tượng OUT PUT

Bài giảng lập trình hướng đối tượng OUT PUT

HỌC VIỆN CÔNG NGHỆ BƯU CHÍNH VIỄN THÔNG

BÀI GIẢNG MÔN

LẬP TRÌNH HƯỚNG ĐỐI TƯỢNG

Giảng viên: Nguyễn Mạnh Sơn

Bộ môn: Công nghệ phần mềm - Khoa CNTT1

Học kỳ/Năm biên soạn: I – 2009/2010

Input và Output

6 Random Access Files

7 Kết hợp giao diện SWING và đọc ghi file

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Files và Directories

File(String path)

File(String directoryPath, String filename)

File(File directory, String filename)

File Constructors

boolean canRead(); boolean canWrite()

boolean delete(); boolean equals(Object obj)

boolean exists(); boolean exists()

String getAbsolutePath();

String getCanonicalPath() throws IOException

String getName(); String getParent()

String getPath(); boolean isAbsolute()

Methods

Lớp File cho phép định nghĩa các

thông tin liên quan đến file và thư

mục

boolean isDirectory()boolean isFile()long lastModified()long length()String[] list()boolean mkdir()boolean mkdirs()boolean renameTo(File newName)

Methods

Files and Directories

// Test Some Methods

File file = new File(args[0]);

getAbsolutePath() = 11\FileDemo.java

getCanonicalPath() = 11\FileDemo.java

D:\lecture\2004-01\teachyourself\example10-getPath() = FileDemo.javacanRead() = true

canWrite() = true

System.out.println("canRead() = " + file.canRead());

System.out.println("canWrite() = " + file.canWrite());

} catch(Exception e) { e.printStackTrace();

} }}

Character Streams

Reader

BufferedReader InputStreamReader StringReader

CharArrayReader PipedReader

FilterReader

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Character Streams

Writer

BufferedWriter OutputStreamWriter StringWriter

CharArrayWriter PipedWriter

FilterWriter PrintWriter

abstract void close() throws IOException

abstract void flush() throws IOException

void write(int c) throws IOException

void write(char buffer[]) throws IOException

abstract void write(char buffer[], int index, int size) throws

IOException

void write(String s) throws IOException

void write(String s, int index, int size) throws IOException

Methods

OutputStreamWriter(OutputStream os)OutputStreamWriter(OutputStream os, String encoding)

FileWriter(String filepath) throws IOException

FileWriter Constructors

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Character Streams

Refer to http://java.sun.com/j2se/1.5.0/docs/api/java/io/Reader.html

abstract void close() throws IOException

void mark(int numChars) throws IOException

boolean markSupported()

int read() throws IOException

int read(char buffer[]) throws IOException

int read(char buffer[], int offset, int numChars) throws

IOException

boolean ready() throws IOException

void reset() throws IOException

int skip(long numChars) throws IOException

Methods của lớp Reader

InputStreamWriter(InputStream os)InputStreamWriter(InputStream os, String encoding)

FileWriter fw = new FileWriter(args[0]);

// Write string to the file

for (int i = 0; i < 12; i++) {

class FileReaderDemo { public static void main(String args[]) { try {

FileReader fr = new FileReader(args[0]);

int i;

while((i = fr.read()) != -1) { System.out.print((char)i);

} fr.close();

} catch(Exception e) { System.out.println("Exception: " + e);

} }}

Run :

java FileWriterDemo output.txt

java FileReaderDemo output.txt

FileWriter fw = new FileWriter(args[0]);

BufferedWriter bw = new BufferedWriter(fw);

for (int i = 0; i < 12; i++) { bw.write("Line " + i + "\n");

} bw.close();

} catch (Exception e) { System.out.println("Exception: " + e);

} }}

Character Stream Examples

class BufferedReaderDemo {

public static void main(String args[]) {

try {

FileReader fr = new FileReader(args[0]);

BufferedReader br = new BufferedReader(fr);

class ReadConsole { public static void main(String args[]) { try {

InputStreamReader isr = new InputStreamReader(System.in);

BufferedReader br = new BufferedReader(isr);

String s;

while((s = br.readLine()) != null) { System.out.println(s.length());

} isr.close();

} catch (Exception e) { System.out.println("Exception: " + e);

} }}

Run :

java BufferedWriterDemo output.txt

java BufferedReaderDemo output.txt

PrintWriter(Writer writer, boolean flushOnNewline)

PrintWriter Constructor class PrintWriterDemo { public static void main(String args[]) {

try { PrintWriter pw = new PrintWriter(System.out);

} }}

Byte Streams (Binary Streams)

Object

InputStream

FileInputStream FilterInputStream

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Byte Streams

InputStream

AutioInputStream FileInputStream ObjectInputStream SequenceInputStream ByteArrayInputStream PipedInputStream

FilterInputStream

Byte Streams

OutputStream

FileOutputStream ObjectOutputStream ByteArrayOutputStream PipeOutputStream

FilterOutputStream

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Byte Streams

Refer to http://java.sun.com/j2se/1.4.2/docs/api/java/io/OutputStream.html

void close() throws IOException

void flush() throws IOException

void write(int i) throws IOException

void write(byte buffer[]) throws IOException

void write(char buffer[], int index, int size) throws

IOException

Methods Defined by the OutputStream

FileOutputStreamWriter(String filepath) throws IOException

FileOutputStreamWriter(String filepath, boolean append)

throws IOException

FileOutputStreamWriter(File fileObj) throws IOException

FileOutputStream Constructor

BufferedOutputStream(OutputStream os)BufferedOutputStream(OutputStream os, int bufSize)

Byte Streams (DataOutput Interface)

Refer tohttp://java.sun.com/j2se/1.5.0/docs/api/java/io/DataOutput.html

void write(int i) throws IOException

void write(byte buffer[]) throws IOException

void write(byte buffer[], int index, int size) throws

IOException

void writeBoolean(boolean b) throws IOException

void writeByte(int i) throws IOException

void writeByte(String s) throws IOException

void writeChar(int i) throws IOException

void writeChars(String s) throws IOException

void writeDouble(double d) throws IOException

void writeFloat(float f) throws IOException

void writeInt(int i) throws IOException

void writeLong(long l) throws IOException

void writeShort(short s) throws IOException

void writeUTF(String s) throws IOException

Methods Defined by the DataOutput

PrintStream(OutputStream outputStream)PrintStream(OutputStream outputStream, boolean flushOnNewline)

PrintStream Constructors

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Byte Streams (InputStream Interface)

Refer tohttp://java.sun.com/j2se/1.5.0/docs/api/java/io/InputStream.html

int available() throws IOException

void close() throws IOException

void mark(int numBytes)

boolean markSupported()

int read() throws IOException

int read(byte buffer[]) throws IOException

int read(byte buffer[], int offset, int numBytes) throws

IOException

Void reset() throws IOException

int skip(long numBytes) throws IOExcepion

Methods Defined by the InputStream

BufferedInputStream Constructors

DataInputStream(InputStream is)

DataInputStream Constructor

Byte Streams (DataInput Interface)

Refer tohttp://java.sun.com/j2se/1.5.0/docs/api/java/io/DataInput.html

boolean readBoolean() throws IOException

byte readByte() throws IOException

char readChar() throws IOException

double read Double() throws IOException

float readFloat() throws IOException

void readFully(byte buffer[]) throws IOException

void readFully(byte buffer[], int index, int size) throws

IOException

int readInt() throws IOException

String readLine() throws IOException

long readLong() throws IOException

short readShort() throws IOException

String readUTF() throws IOException

int readUnsignedByte() throws IOException

int readUnsignedShort() throws IOException

int skipBytes(int n) throws IOException

Methods Defined by DataInput class FileOutputStreamDemo {

public static void main(String args[]) { try {

FileOutputStream fos = new FileOutputStream(args[0]);

for (int i = 0; i < 12; i++) { fos.write(i);

} fos.close();

} catch (Exception e) { System.out.println("Exception: " + e);

} }}

Run :

java FileOutputStreamDemo output.txtjava FileInputStreamDemo output.txt

FileInputStream fis = new FileInputStream(args[0]);

BufferedInputStream bis = new BufferedInputStream(fis);

int i;

while((i = bis.read()) != -1) { System.out.println(i);

} fis.close();

} catch (Exception e) { System.out.println("Exception: " + e);

} }}

Run :

java BufferedOutputStreamDemo output.txt

java BufferedInputStreamDemo output.txt

FileInputStream fis = new FileInputStream(args[0]);

DataInputStream dis = new DataInputStream(fis);

} }}

Run :

java DataOutputStreamDemo output.txt

java DataInputStreamDemo output.txt

Random Access Files

Refer

tohttp://java.sun.com/j2se/1.5.0/docs/api/java/io/RandomAcces

sFile.html

void close() throws IOException

long getFilePointer() throws IOException

long length() throws IOException

int read() throws IOException

int read(byte buffer[], int index, int size) throws

IOException

int read(byte buffer[]) throws IOException

void seek(long n) throws IOException

int skipBytes(int n) throws IOException

Methods Defined by the RandomAccessFile long position = raf.length(); position -= count;

if (position < 0) position = 0;

raf.seek(position);

while(true) { try {

byte b = raf.readByte();

System.out.print((char)b);

} catch (EOFException eofe) { break;

} } } catch (Exception e) { e.printStackTrace();

} }}

12/09/12 26

Kết hợp giao diện và đọc ghi file

• Vấn đề: Kết hợp giao diện SWING để xây dựng ứng dụng

đọc và ghi file

• Viết chương trình tạo ra giao diện như dưới đây:

Kết hợp giao diện và đọc ghi file

private boolean _clickMeMode = true;

FileIO() { //Begin Constructor

text = new JLabel("Doan van ban ghi vao file:");

button = new JButton("Ghi vao file");

button.addActionListener(this);

textField = new JTextField(30);

panel = new JPanel();

public void actionPerformed(ActionEvent event){

Object source = event.getSource();

if (source == button) { String s = null;

//Write

if (_clickMeMode){

try { String text = textField.getText();

byte b[] = text.getBytes();

String outputFileName = System.getProperty("user.home", File.separatorChar + "home" +

File.separatorChar + "zelda") + File.separatorChar + "text.txt";

FileOutputStream out = new FileOutputStream(outputFileName); out.write(b);

out.close();

} catch(java.io.IOException e) { System.out.println("Khong the ghi vao file text.txt");

} //Read try { String inputFileName = System.getProperty("user.home", File.separatorChar + "home" +

File.separatorChar + "zelda") + File.separatorChar + "text.txt";

File inputFile = new File(inputFileName);

FileInputStream in = new FileInputStream(inputFile);

byte bt[] = new byte[(int)inputFile.length()];

in.read(bt);

//Save text to file

text.setText("Doan van ban ghi vao file:");

textField.setText("");

button.setText("Ghi vao file");

_clickMeMode = true;

} } }

public static void main(String[] args){

FileIO frame = new FileIO();

frame.setTitle("Example");

WindowListener l = new WindowAdapter() {

public void windowClosing(WindowEvent e) {

Xử lý ngoại lệ

Luôn luôn thực hiện

finally { System.out.println("Finally block");

} }}

Result : java Divider 1 0Before Division

ArithmeticExceptionFinally block

b: finallyAfter ba: finallyAfter a

public static void b() { try {

System.out.println("Before c");

c();

System.out.println("After c");

} catch (ArrayIndexOutOfBoundsException e) { System.out.println("b: " + e);

} finally { System.out.println("b: finally");

} }

public static void c() { try {

System.out.println("Before d");

d();

System.out.println("After d");

} catch (NumberFormatException e) { System.out.println("c: " + e);

} finally { System.out.println("c: finally");

} }

public static void d() { try {

int array[] = new int[4];

array[10] = 10;

} catch (ClassCastException e) { System.out.println("d: " + e);

} finally { System.out.println("d: finally");

} }}

Thực hiện với các Exception

throw new ExceptionType(args);

Với Exception được tạo mới

Từ khoá Throw (tiếp)

c: java.lang.ArithmeticException: / by zeroc: finally

b: java.lang.ArithmeticException: / by zerob: finally

After ba: finallyAfter a

public static void b() { try {

System.out.println("Before c");

c();

System.out.println("After c");

} catch (ArithmeticException e) { System.out.println("b: " + e);

} finally { System.out.println("b: finally");

} }

public static void c() { try {

System.out.println("Before d");

d();

System.out.println("After d");

} catch (ArithmeticException e) { System.out.println("c: " + e);

throw e;

} finally { System.out.println("c: finally");

} }

public static void d() { try {

int i = 1;

int j = 0;

System.out.println("Before division"); System.out.println(i / j);

System.out.println("After division"); }

catch (ArithmeticException e) { System.out.println("d: " + e);

throw e;

} finally { System.out.println("d: finally");

} }}

After amain: finally

public static void a() { try {

System.out.println("Before throw statement");

throw new ArithmeticException();

} catch (Exception e) { System.out.println("a: " + e);

} finally { System.out.println("a: finally");

} }}

ClassCastException NegativeArraySizeException NullPointerException

NumberFromatException SecurityException

StringIndexOutOfBoundsException

} } public static void d() { try {

int i = 1;

int j = 0;

System.out.println(i / j);

} catch (NullPointerException e) { e.printStackTrace();

} }}

} else { throw new ExceptionB("We have a big problem");

} } }class ExceptionA extends Exception { public ExceptionA(String message) { super(message);

}}

class ExceptionB extends Exception { public ExceptionB(String message) { super(message);

}}

12/09/12 40

Applet

Giới thiệu APPLET

 Là một chương trìnhJava mà chạy với sự hỗ trợ của trình duyệt web•

 Tất cả các applets là lớp con của lớp‘Applet’•

 Để tạo một applet, bạncầnimport hai gói sau:

 java.applet

 java.awt

12/09/12 42

Cấu trúc applet

 Định nghĩa một applet từ bốn sự kiện xảy ra trong quá trình thực thi

 Mỗi sự kiện được định nghĩa bởi một phương thức tương ứng.