Java IO. Streams

Язык Java

Потоки
java.io

Алексей Бованенко

Введение

Понятие потоков

Поток представляет собой набор данных, связанный с источником (поток ввода), либо приемником (поток вывода)

Источник или приемник

Файлы на диске

Устройства

Другие программы

Буфер в памяти

Потоки могут содержать данные различных типов

Примитивные типы

Символы

Объектные потоки

Потоки в java.io

В java.io определены следующие потоки

InputStream / OutputStream

FileInputStream / FileOutputStream

BufferedInputStream / BufferedOutputStream

InputStreamReader / OutputStreamWriter

FileReader / FileWriter

BufferedReader / BufferedWriter

StringReader / StringWriter

DataInputStream / DataOutputStream

ObjectInputStream / ObjectOutputStream

FileInputStream

class FileInputStream extends InputStream

public FileInputStream(String name) throws FileNotFoundException

public FileInputStream(File file) throws FileNotFoundException

public FileInputStream(FileDescriptor fdObj)

public native int read() throws IOException

private native int readBytes(byte b[], int off, int len) throws IOException

public int read(byte b[]) throws IOException

public int read(byte b[], int off, int len) throws IOException

public native long skip(long n) throws IOException

public native int available() throws IOException

public void close() throws IOException

public FileChannel getChannel()

public boolean markSupported()

public synchronized void reset() throws IOException

public synchronized void mark(int readlimit)

FileOutputStream

class FileOutputStream extends OutputStream

public FileOutputStream(String name) throws FileNotFoundException

public FileOutputStream(String name, boolean append) throws FileNotFoundException

public FileOutputStream(File file) throws FileNotFoundException

public FileOutputStream(File file, boolean append) throws FileNotFoundException

public FileOutputStream(FileDescriptor fdObj)

public native void write(int b) throws IOException

public void write(byte b[]) throws IOException

public void write(byte b[], int off, int len) throws IOException


public void flush() throws IOException

Пример использования (использование методов read() и write(int))

try{ // Внешний блок try try{ // Создание потока вывода fo=new FileOutputStream("out.txt"); int l=s.length(); int i=0; while(i<l) { fo.write(s.codePointAt(i++)); } }finally{ if(fo!=null) fo.close(); }

Пример (продолжение)

try{ // Создание входного потока fi=new FileInputStream("out.txt"); int i=0; StringBuilder sb=new StringBuilder(); while((i=fi.read())!=-1) { sb.append(Character.toChars(i)); } System.out.println("Received from file: "+sb.toString()); }finally{ if(fi!=null) fi.close(); } }catch(FileNotFoundException e) // Перехват для внешнего try { System.out.println(e); }catch(IOException e) // Перехват для внешнего try { System.out.println(e); }

Пример использования (использование методов read(byte[]) и write(byte[]))

try{ // Внешний блок try try{ // Создание потока вывода fo=new FileOutputStream("out.txt"); int l=s.length(); int i=0; byte[] b=s.getBytes(); fo.write(b); }finally{ if(fo!=null) fo.close(); }


try{ // Создание входного потока fi=new FileInputStream("out.txt"); int i=fi.available(); byte[] b=new byte[i]; fi.read(b); String s1=new String(b); System.out.println("Received from file: "+s1); }finally{ if(fi!=null) fi.close(); } }catch(FileNotFoundException e) // Перехват для внешнего try { System.out.println(e); }catch(IOException e) // Перехват для внешнего try { System.out.println(e); }

Пример использования (использование методов read(byte[], int, int) и write(byte[], int , int))

try{ // Внешний блок try try{ // Создание потока вывода fo=new FileOutputStream("out.txt"); int l=s.length(); int i=0; byte[] b=s.getBytes(); fo.write(b,0,b.length); }finally{ if(fo!=null) fo.close(); }


try{ // Создание входного потока fi=new FileInputStream("out.txt"); int i=fi.available(); byte[] b=new byte[i]; fi.read(b,0,i); String s1=new String(b); System.out.println("Received from file: "+s1); }finally{ if(fi!=null) fi.close(); } }catch(FileNotFoundException e) // Перехват для внешнего try { System.out.println(e); }catch(IOException e) // Перехват для внешнего try { System.out.println(e); }

BufferedInputStream

class BufferedInputStream extends FilterInputStream

public BufferedInputStream(InputStream in)

public BufferedInputStream(InputStream in, int size)

public synchronized int read() throws IOException

public synchronized int read(byte b[], int off, int len) throws IOException

public synchronized long skip(long n) throws IOException

public synchronized int available() throws IOException

public synchronized void mark(int readlimit)

public synchronized void reset() throws IOException



BufferedOutputStream

class BufferedOutputStream extends FilterOutputStream

public BufferedOutputStream(OutputStream out)

public BufferedOutputStream(OutputStream out, int size)

public synchronized void write(int b) throws IOException

public synchronized void write(byte b[], int off, int len) throws IOException

public synchronized void flush() throws IOException

Пример использования BufferedInputStream/BufferedOutputStream

try{ // Внешний блок try try{ // Создание потока для записи файла bo=new BufferedOutputStream(new FileOutputStream("out.txt")); byte[] b=new byte[s.length()]; b=s.getBytes(); bo.write(b,0,b.length); }finally{ if(bo!=null) bo.close(); }

Пример использования (продолжение)

try{ // Создание потока для чтения bi=new BufferedInputStream(new FileInputStream("out.txt")); int i=bi.available(); byte[] b=new byte[i]; bi.mark(i); bi.read(b, 0, i); bi.reset(); String s1=new String(b); bi.read(b, 0, i); String s2=new String(b); System.out.println(s1+" "+s2); }finally{ if(bi!=null) bi.close(); } }catch(Exception e){ // Перехват для внешнего try System.out.println(e); }

InputStreamReader

public class InputStreamReader extends Reader

public InputStreamReader(InputStream in)

public InputStreamReader(InputStream in, String charsetName)

public InputStreamReader(InputStream in, Charset cs)

public InputStreamReader(InputStream in, CharsetDecoder dec)

public String getEncoding()

public int read() throws IOException

public int read(char cbuf[]) throws IOException

public int read(char cbuf[], int offset, int length) throws IOException

public boolean ready() throws IOException


OutputStreamWriter

class OutputStreamWriter extends Writer

public OutputStreamWriter(OutputStream out, String charsetName) throws UnsupportedEncodingException

public OutputStreamWriter(OutputStream out)

public OutputStreamWriter(OutputStream out, Charset cs)

public OutputStreamWriter(OutputStream out, CharsetEncoder enc)

public String getEncoding()

public void write(int c) throws IOException

public void write(char cbuf[], int off, int len) throws IOException

public void write(String str) throws IOException

public void write(String str, int off, int len) throws IOException



Пример использования OutputStreamWriter/InputStreamReader

try{ // Внешний блок try try{ // Создания потока для записи данных or=new OutputStreamWriter(new BufferedOutputStream(new FileOutputStream("out.txt")),"KOI8-R"); or.write(s); }finally{ if(or!=null) or.close(); }


try{ // Создание потока для чтения данных ir=new InputStreamReader(new BufferedInputStream(new FileInputStream("out.txt")),"KOI8-R"); char[] b=new char[1024]; int i=0; StringBuilder sb=new StringBuilder(); while((i=ir.read(b))!=-1) { sb.append(b, 0, i); } System.out.println("Result: "+sb.toString()); }finally{ if(ir!=null) ir.close(); } }catch(Exception e) // Перехват для внешнего try { System.out.println(e); }

FileReader

class FileReader extends InputStreamReader

public FileReader(String fileName) throws FileNotFoundException

public FileReader(File file) throws FileNotFoundException

public FileReader(FileDescriptor fd)

FileWriter

class FileWriter extends OutputStreamWriter

public FileWriter(String fileName) throws IOException

public FileWriter(String fileName, boolean append) throws IOException

public FileWriter(File file) throws IOException

public FileWriter(File file, boolean append) throws IOException

public FileWriter(FileDescriptor fd)

Пример использования FileReader и FileWriter

try{ // Внешний блок try try{ // Создание файла fw=new FileWriter("out.txt"); fw.write(s);

}finally{

if(fw!=null)

fw.close();

}


try{

fr=new FileReader("out.txt");

char[] b=new char[1024];

int i=0;

StringBuilder sb=new StringBuilder();

while((i=fr.read(b))!=-1)

{

sb.append(b, 0, i);

}

System.out.println(sb.toString());

}finally{

if(fr!=null)

fr.close();

}

}catch(Exception e)

{

System.out.println(e);

}

BufferedReader

class BufferedReader extends Reader

public BufferedReader(Reader in, int sz)

public BufferedReader(Reader in)

public int read() throws IOException

public int read(char cbuf[], int off, int len) throws IOException

String readLine(boolean ignoreLF) throws IOException

public String readLine() throws IOException

public long skip(long n) throws IOException

public boolean ready() throws IOException


public void mark(int readAheadLimit) throws IOException

public void reset() throws IOException


BufferedWriter

class BufferedWriter extends Writer

public BufferedWriter(Writer out)

public BufferedWriter(Writer out, int sz)

public void write(int c) throws IOException

public void write(char cbuf[], int off, int len) throws IOException

public void write(String s, int off, int len) throws IOException

public void newLine() throws IOException



Пример использования BufferedReader/BufferedWriter

try{ // Внешний блок try try{ // Создание потока для записи bw=new BufferedWriter(new FileWriter("out.txt")); bw.write(s); }finally{ if(bw!=null) bw.close(); } try{ // Создание потока для чтения br=new BufferedReader(new FileReader("out.txt")); String s1=br.readLine(); System.out.println(s1); }finally{ if(br!=null) br.close(); } }catch(Exception e) // Обработка исключений для внешнего try { System.out.println(e); }

DataInputStream

class DataInputStream extends FilterInputStream implements DataInput

public DataInputStream(InputStream in)

void readFully(byte b[]) throws IOException

void readFully(byte b[], int off, int len) throws IOException

int skipBytes(int n) throws IOException

boolean readBoolean() throws IOException

byte readByte() throws IOException

int readUnsignedByte() throws IOException

short readShort() throws IOException

int readUnsignedShort() throws IOException

char readChar() throws IOException

int readInt() throws IOException

long readLong() throws IOException

float readFloat() throws IOException

double readDouble() throws IOException

String readLine() throws IOException

DataOutputStream

class DataOutputStream extends FilterOutputStream implements DataOutput

public DataOutputStream(OutputStream out)

void write(int b) throws IOException

void write(byte b[]) throws IOException

void write(byte b[], int off, int len) throws IOException

void writeBoolean(boolean v) throws IOException

void writeByte(int v) throws IOException

void writeShort(int v) throws IOException

void writeChar(int v) throws IOException

void writeInt(int v) throws IOException

void writeLong(long v) throws IOException

void writeFloat(float v) throws IOException

void writeDouble(double v) throws IOException

void writeBytes(String s) throws IOException

void writeChars(String s) throws IOException

Пример использования DataInputStream/DataOutputStream

int i=10; char c='a'; boolean b=true; float f=10.6f; String s="Hello"; try{ try{ dout=new DataOutputStream(new FileOutputStream("out2.txt")); dout.writeInt(i); dout.writeChar(c); dout.writeBoolean(b); dout.writeFloat(f); dout.writeUTF(s); }finally{ if(dout!=null) dout.close(); }


try{ di=new DataInputStream(new FileInputStream("out2.txt")); int j=di.readInt(); char c1=di.readChar(); boolean b1=di.readBoolean(); float f1=di.readFloat(); String s1=di.readUTF(); System.out.println("Int: "+j+" char: "+c1+" bool: "+b1+" float: "+f1+" Str: "+s1); }finally{ if(di!=null) di.close(); } }catch(Exception e) { System.out.println(e); }

ObjectInputStream

class ObjectInputStream extends InputStream implements ObjectInput, ObjectStreamConstants

public ObjectInputStream(InputStream in) throws IOException

public final Object readObject() throws IOException, ClassNotFoundException

ObjectOutputStream

class ObjectOutputStream extends OutputStream implements ObjectOutput, ObjectStreamConstants

public ObjectOutputStream(OutputStream out) throws IOException

public final void writeObject(Object obj) throws IOException

Пример использования ObjectInputStream/ObjectOutputStream

TestClass tc=new TestClass(10,"Hello, world"); System.out.println(tc); try{ try{ oo=new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream("out3.txt"))); oo.writeObject(tc); }finally{ if(oo!=null) oo.close(); } try{ oi=new ObjectInputStream(new BufferedInputStream(new FileInputStream("out3.txt"))); TestClass ttt=(TestClass)oi.readObject(); System.out.println(ttt); }finally{ if(oi!=null) oi.close(); } }catch(Exception e){ System.out.println(e); }

Конец

Вопросы
e-mail: a.bovanenko@gmail.com

Java IO. Streams

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