彻底明白Java的IO系统
来源:互联网 发布:黑马程序员深圳校区 编辑:程序博客网 时间:2024/06/07 01:35
一. Input和Output
1. stream代表的是任何有能力产出数据的数据源,或是任何有能力接收数据的接收源。在Java的IO中,所有的stream(包括Input和Out stream)都包括两种类型:
1.1 以字节为导向的stream
以字节为导向的stream,表示以字节为单位从stream中读取或往stream中写入信息。以字节为导向的stream包括下面几种类型:
1) input stream:
1) ByteArrayInputStream:把内存中的一个缓冲区作为InputStream使用
2) StringBufferInputStream:把一个String对象作为InputStream
3) FileInputStream:把一个文件作为InputStream,实现对文件的读取操作
4) PipedInputStream:实现了pipe的概念,主要在线程中使用
5) SequenceInputStream:把多个InputStream合并为一个InputStream
2) Out stream
1) ByteArrayOutputStream:把信息存入内存中的一个缓冲区中
2) FileOutputStream:把信息存入文件中
3) PipedOutputStream:实现了pipe的概念,主要在线程中使用
4) SequenceOutputStream:把多个OutStream合并为一个OutStream
1.2 以Unicode字符为导向的stream
以Unicode字符为导向的stream,表示以Unicode字符为单位从stream中读取或往stream中写入信息。以Unicode字符为导向的stream包括下面几种类型:
1) Input Stream
1) CharArrayReader:与ByteArrayInputStream对应
2) StringReader:与StringBufferInputStream对应
3) FileReader:与FileInputStream对应
4) PipedReader:与PipedInputStream对应
2) Out Stream
1) CharArrayWrite:与ByteArrayOutputStream对应
2) StringWrite:无与之对应的以字节为导向的stream
3) FileWrite:与FileOutputStream对应
4) PipedWrite:与PipedOutputStream对应
以 字符为导向的stream基本上对有与之相对应的以字节为导向的stream。两个对应类实现的功能相同,字是在操作时的导向不同。如 CharArrayReader:和ByteArrayInputStream的作用都是把内存中的一个缓冲区作为InputStream使用,所不同的 是前者每次从内存中读取一个字节的信息,而后者每次从内存中读取一个字符。
1.3 两种不现导向的stream之间的转换
InputStreamReader和OutputStreamReader:把一个以字节为导向的stream转换成一个以字符为导向的stream。
2. stream添加属性
2.1 “为stream添加属性”的作用
运用上面介绍的Java中操作IO的API,我们就可完成我们想完成的任何操作了。但通过FilterInputStream和FilterOutStream的子类,我们可以为stream添加属性。下面以一个例子来说明这种功能的作用。
如果我们要往一个文件中写入数据,我们可以这样操作:
FileOutStream fs = new FileOutStream(“test.txt”);
然 后就可以通过产生的fs对象调用write()函数来往test.txt文件中写入数据了。但是,如果我们想实现“先把要写入文件的数据先缓存到内存中, 再把缓存中的数据写入文件中”的功能时,上面的API就没有一个能满足我们的需求了。但是通过FilterInputStream和 FilterOutStream的子类,为FileOutStream添加我们所需要的功能。
2.2 FilterInputStream的各种类型
2.2.1 用于封装以字节为导向的InputStream
1) DataInputStream:从stream中读取基本类型(int、char等)数据。
2) BufferedInputStream:使用缓冲区
3) LineNumberInputStream:会记录input stream内的行数,然后可以调用getLineNumber()和setLineNumber(int)
4) PushbackInputStream:很少用到,一般用于编译器开发
2.2.2 用于封装以字符为导向的InputStream
1) 没有与DataInputStream对应的类。除非在要使用readLine()时改用BufferedReader,否则使用DataInputStream
2) BufferedReader:与BufferedInputStream对应
3) LineNumberReader:与LineNumberInputStream对应
4) PushBackReader:与PushbackInputStream对应
2.3 FilterOutStream的各种类型
2.2.3 用于封装以字节为导向的OutputStream
1) DataIOutStream:往stream中输出基本类型(int、char等)数据。
2) BufferedOutStream:使用缓冲区
3) PrintStream:产生格式化输出
2.2.4 用于封装以字符为导向的OutputStream
1) BufferedWrite:与对应
2) PrintWrite:与对应
3. RandomAccessFile
1) 可通过RandomAccessFile对象完成对文件的读写操作
2) 在产生一个对象时,可指明要打开的文件的性质:r,只读;w,只写;rw可读写
3) 可以直接跳到文件中指定的位置
4. I/O应用的一个例子
import java.io.*;
public class TestIO{
public static void main(String[] args)
throws IOException{
//1.以行为单位从一个文件读取数据
BufferedReader in =
new BufferedReader(
new FileReader("F://nepalon//TestIO.java"));
String s, s2 = new String();
while((s = in.readLine()) != null)
s2 += s + "/n";
in.close();
//1b. 接收键盘的输入
BufferedReader stdin =
new BufferedReader(
new InputStreamReader(System.in));
System.out.println("Enter a line:");
System.out.println(stdin.readLine());
//2. 从一个String对象中读取数据
StringReader in2 = new StringReader(s2);
int c;
while((c = in2.read()) != -1)
System.out.println((char)c);
in2.close();
//3. 从内存取出格式化输入
try{
DataInputStream in3 =
new DataInputStream(
new ByteArrayInputStream(s2.getBytes()));
while(true)
System.out.println((char)in3.readByte());
}
catch(EOFException e){
System.out.println("End of stream");
}
//4. 输出到文件
try{
BufferedReader in4 =
new BufferedReader(
new StringReader(s2));
PrintWriter out1 =
new PrintWriter(
new BufferedWriter(
new FileWriter("F://nepalon// TestIO.out")));
int lineCount = 1;
while((s = in4.readLine()) != null)
out1.println(lineCount++ + ":" + s);
out1.close();
in4.close();
}
catch(EOFException ex){
System.out.println("End of stream");
}
//5. 数据的存储和恢复
try{
DataOutputStream out2 =
new DataOutputStream(
new BufferedOutputStream(
new FileOutputStream("F://nepalon// Data.txt")));
out2.writeDouble(3.1415926);
out2.writeChars("/nThas was pi:writeChars/n");
out2.writeBytes("Thas was pi:writeByte/n");
out2.close();
DataInputStream in5 =
new DataInputStream(
new BufferedInputStream(
new FileInputStream("F://nepalon// Data.txt")));
BufferedReader in5br =
new BufferedReader(
new InputStreamReader(in5));
System.out.println(in5.readDouble());
System.out.println(in5br.readLine());
System.out.println(in5br.readLine());
}
catch(EOFException e){
System.out.println("End of stream");
}
//6. 通过RandomAccessFile操作文件
RandomAccessFile rf =
new RandomAccessFile("F://nepalon// rtest.dat", "rw");
for(int i=0; i<10; i++)
rf.writeDouble(i*1.414);
rf.close();
rf = new RandomAccessFile("F://nepalon// rtest.dat", "r");
for(int i=0; i<10; i++)
System.out.println("Value " + i + ":" + rf.readDouble());
rf.close();
rf = new RandomAccessFile("F://nepalon// rtest.dat", "rw");
rf.seek(5*8);
rf.writeDouble(47.0001);
rf.close();
rf = new RandomAccessFile("F://nepalon// rtest.dat", "r");
for(int i=0; i<10; i++)
System.out.println("Value " + i + ":" + rf.readDouble());
rf.close();
}
}
关于代码的解释(以区为单位):
1区中,当读取文件时,先把文件内容读到缓存中,当调用in.readLine()时,再从缓存中以字符的方式读取数据(以下简称“缓存字节读取方式”)。
1b区中,由于想以缓存字节读取方式从标准IO(键盘)中读取数据,所以要先把标准IO(System.in)转换成字符导向的stream,再进行BufferedReader封装。
2区中,要以字符的形式从一个String对象中读取数据,所以要产生一个StringReader类型的stream。
4区中,对String对象s2读取数据时,先把对象中的数据存入缓存中,再从缓冲中进行读取;对TestIO.out文件进行操作时,先把格式化后的信息输出到缓存中,再把缓存中的信息输出到文件中。
5 区中,对Data.txt文件进行输出时,是先把基本类型的数据输出屋缓存中,再把缓存中的数据输出到文件中;对文件进行读取操作时,先把文件中的数据读 取到缓存中,再从缓存中以基本类型的形式进行读取。注意in5.readDouble()这一行。因为写入第一个writeDouble(),所以为了正 确显示。也要以基本类型的形式进行读取。
6区是通过RandomAccessFile类对文件进行操作。
**************************************************************************************************
重要提示:
LineNumberInputStream,StringBufferInputStream已经废除!大家不要再用!
StringBufferInputStream,This class does not properly convert characters into bytes!
StringBufferInputStream,Deprecated. This class incorrectly assumes that bytes adequately represent characters!
**************************************************************************************************
DataInputStream流中已经没有readLine()整个方法!
替换为: BufferedReader d=new BufferedReader(new InputStreamReader(in));
--------把字节流转换为字符流接入缓存读取字符流中,再进行处理!
这个方法很大的优势!
**************************************************************************************************
-------------------------------------------------------------------
----------标准设备System.in读取数据------------------
读取字节:BufferedInputStream
读取字符:BufferedReader + InputStreamReader
----------------------------------------------
import java.io.*;
public class systemin
{
public static void main(String args[])
{ try{ //流转换!
BufferedReader is=new BufferedReader(new InputStreamReader(System.in))
String inputline=null;
while((inputline=is.readLine())!=null)
System.out.println(inputline);
is.close();
}
catch(IOException e)
{ System,out.println("IOXE: "+e);
}
}
}
----------------------------------------------------------------------------------------------
-----------------标准输出System.out是一个打印流PrintStream-----------
import java.io.*;
public class PrintStandardOutput {
public static void main(String[] args) {
String myAnswer = "No, and that's final,";
System.out.println("Hello World of Java");
System.out.println("The answer is " + myAnswer + " at this time.");
PrintWriter pw = new PrintWriter(System.out);
pw.println("The answer is " + myAnswer + " at this time.");
int i = 42;
pw.println(i + '=' + " the answer.");
pw.println("Note: " + i + '=' + " the answer.");
pw.println(i + "=" + " the answer.");
pw.println(i + ('=' + " the answer."));
pw.close();
}
}
-------------------------------------------------------------------------------------------------
-----------------------要读取(输出到—)一个文本文件-----------------------------
BufferedReader is=new BufferedReader(new FileReader("xxxx.text"));读取
BufferedOutputStream byteout=new BufferedOutputStream(new FileOutputStream("XX.dat"));
// 写出到文本!
-------------------------------------------------------------
import java.io.*;
public class OpenFileByName {
public static void main(String[] args) throws IOException {
BufferedReader is = new BufferedReader(new FileReader("myFile.txt"));
BufferedOutputStream bytesOut = new BufferedOutputStream(
new FileOutputStream("bytes.dat"));
// Code here to read from is, write to bytesOut
bytesOut.close();
}
}
-------------------------------------------------------------
import java.io.*;
public class FileIO {
private FileIO() { }
public static void copyFile(String inName, String outName)
throws FileNotFoundException, IOException {
BufferedInputStream is =
new BufferedInputStream(new FileInputStream(inName));
BufferedOutputStream os =
new BufferedOutputStream(new FileOutputStream(outName));
copyFile(is, os, true);
}
/** Copy a file from an opened InputStream to opened OutputStream */
public static void copyFile(InputStream is, OutputStream os, boolean close)
throws IOException {
int b;while ((b = is.read()) != -1) {
os.write(b);
}
is.close();
if (close)
os.close();
}
public static void copyFile(Reader is, Writer os, boolean close)
throws IOException {
int b;while ((b = is.read()) != -1) {
os.write(b);
}
is.close();
if (close)
os.close();
}
public static void copyFile(String inName, PrintWriter pw, boolean close)
throws FileNotFoundException, IOException {
BufferedReader is = new BufferedReader(new FileReader(inName));
copyFile(is, pw, close);
}
public static String readLine(String inName)
throws FileNotFoundException, IOException {
BufferedReader is = new BufferedReader(new FileReader(inName));
String line = null;
line = is.readLine();
is.close();
return line;
}
protected static final int BLKSIZ = 8192;
public void copyFileBuffered(String inName, String outName) throws
FileNotFoundException, IOException {
InputStream is = new FileInputStream(inName);
OutputStream os = new FileOutputStream(outName);
int count = 0;
byte b[] = new byte[BLKSIZ];
while ((count = is.read(b)) != -1) {
os.write(b, 0, count);
}
is.close();
os.close();
}
public static String readerToString(Reader is) throws IOException {
StringBuffer sb = new StringBuffer();
char[] b = new char[BLKSIZ];
int n;
while ((n = is.read(b)) > 0) {
sb.append(b, 0, n);
}
return sb.toString();
}
public static String inputStreamToString(InputStream is)
throws IOException {
return readerToString(new InputStreamReader(is));
}
public static void stringToFile(String text, String fileName)
throws IOException {
BufferedWriter os = new BufferedWriter(new FileWriter(fileName));
os.write(text);
os.flush();
os.close();
}
public static BufferedReader openFile(String fileName)
throws IOException {
return new BufferedReader(new FileReader(fileName));
}
}
-------------------------------------------------------------
import java,io.*;
class fileprocess
{
public static void main(String args[])
{
int b;
byte buffer[]=new byte[1000];
try
{ b=System.out.read(buffer); //存取数据,以备写出!
FileOutputStream out=new FileOotputStream("line.text");
out.write(buffer,0,b); //写出!注意字节缓冲语文件流的关系
]
catch(IOException e)
{ System.out.println(" error");
}
]
}
-------------------------------------------------------------
import java,io.*;
public class read
{
public static void main(String args[]0
{
int b;
byte buffer=new byte[2000];
try
{ FileInputStream readfile=new FileInputStream("XXXX.java");
b=readfile(buffer,0,25000);
try{String str=nre String(buffer,0,b,"Default");//构造String对象!
System.out.println(str);}
catch(UnsuportedEncodeingException e)
{ e.printStackTrace();}
catch( IOException e)
{ System.out.println(" error");}
}
}
-------------------------------------------------------------------------------------------
--------------利用 BufferedReader--FileReader读取文本文件!--------
---------------在IO中始终要注意是字节流还是字符流----------------------
--------------------------------------------------------------------------------------------
import java.io.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
class filewindow extends JFrame implements ActionListener
{
JTextArea text;
BufferedReader in;
JButton button;
FileReader file;
filewindow()
{
super("文件字符流");
Container con=getContentPane();
text=new JTextArea(50,50);
text.setBackground(Color.blue);
try{
File f=new File("E://a.txt");
file=new FileReader(f);
in=new BufferedReader(file);
/**BufferedReader(Reader in)构造函数,
*文件自字符读取流FileReader接入BufferedReader
*流中,以便用BufferedReader的对象方法readLine()高效成行读取!
*/
}
catch(FileNotFoundException e){}
catch(IOException e){}
button=new JButton("读取");
button.addActionListener(this);
con.setLayout(new BorderLayout());
setSize(300,200);
setVisible(true);
con.add(text,"Center");
con.add(button,"South");
addWindowListener(new WindowAdapter()
{public void windowClosing(WindowEvent e)
{setVisible(false);System.exit(0);}});
}
public void actionPerformed(ActionEvent e)
{
String s;
if(e.getSource()==button)
try{
while((s=in.readLine())!=null)
text.append(s+'/n');
//在这里大家还可以用BufferString来暂时保存读取的字符数据!
}
catch(IOException e1){}
}
//---------main()----------
public static void main(String args[])
{
filewindow win=new filewindow();
win.pack();
}
}
-------------------------------------------------------------------------------------------
-------------------RandomAccessFile随机读取文件---------------
import java.io.*;
public class RandomRead
{
final static String FILENAME="E://a.txt";
protected String fileName;
protected RandomAccessFile seeker;
public static void main(String[] argv) throws IOException {
RandomRead r = new RandomRead(FILENAME);
System.out.println("Offset is " + r.readOffset());
System.out.println("Message is /"" + r.readMessage() + "/".");
}
/** Constructor: save filename, construct RandomAccessFile */
public RandomRead(String fname) throws IOException {
fileName = fname;
seeker = new RandomAccessFile(fname, "rw");
}
/** Read the Offset field, defined to be at location 0 in the file. */
public int readOffset() throws IOException {
seeker.seek(0);
seeker.writeChars(FILENAME);// move to very beginning
return seeker.readInt();// and read the offset
}
/** Read the message at the given offset */
public String readMessage() throws IOException {
seeker.seek(120);// move to where
return seeker.readLine();// and read the String
}
}
1. stream代表的是任何有能力产出数据的数据源,或是任何有能力接收数据的接收源。在Java的IO中,所有的stream(包括Input和Out stream)都包括两种类型:
1.1 以字节为导向的stream
以字节为导向的stream,表示以字节为单位从stream中读取或往stream中写入信息。以字节为导向的stream包括下面几种类型:
1) input stream:
1) ByteArrayInputStream:把内存中的一个缓冲区作为InputStream使用
2) StringBufferInputStream:把一个String对象作为InputStream
3) FileInputStream:把一个文件作为InputStream,实现对文件的读取操作
4) PipedInputStream:实现了pipe的概念,主要在线程中使用
5) SequenceInputStream:把多个InputStream合并为一个InputStream
2) Out stream
1) ByteArrayOutputStream:把信息存入内存中的一个缓冲区中
2) FileOutputStream:把信息存入文件中
3) PipedOutputStream:实现了pipe的概念,主要在线程中使用
4) SequenceOutputStream:把多个OutStream合并为一个OutStream
1.2 以Unicode字符为导向的stream
以Unicode字符为导向的stream,表示以Unicode字符为单位从stream中读取或往stream中写入信息。以Unicode字符为导向的stream包括下面几种类型:
1) Input Stream
1) CharArrayReader:与ByteArrayInputStream对应
2) StringReader:与StringBufferInputStream对应
3) FileReader:与FileInputStream对应
4) PipedReader:与PipedInputStream对应
2) Out Stream
1) CharArrayWrite:与ByteArrayOutputStream对应
2) StringWrite:无与之对应的以字节为导向的stream
3) FileWrite:与FileOutputStream对应
4) PipedWrite:与PipedOutputStream对应
以 字符为导向的stream基本上对有与之相对应的以字节为导向的stream。两个对应类实现的功能相同,字是在操作时的导向不同。如 CharArrayReader:和ByteArrayInputStream的作用都是把内存中的一个缓冲区作为InputStream使用,所不同的 是前者每次从内存中读取一个字节的信息,而后者每次从内存中读取一个字符。
1.3 两种不现导向的stream之间的转换
InputStreamReader和OutputStreamReader:把一个以字节为导向的stream转换成一个以字符为导向的stream。
2. stream添加属性
2.1 “为stream添加属性”的作用
运用上面介绍的Java中操作IO的API,我们就可完成我们想完成的任何操作了。但通过FilterInputStream和FilterOutStream的子类,我们可以为stream添加属性。下面以一个例子来说明这种功能的作用。
如果我们要往一个文件中写入数据,我们可以这样操作:
FileOutStream fs = new FileOutStream(“test.txt”);
然 后就可以通过产生的fs对象调用write()函数来往test.txt文件中写入数据了。但是,如果我们想实现“先把要写入文件的数据先缓存到内存中, 再把缓存中的数据写入文件中”的功能时,上面的API就没有一个能满足我们的需求了。但是通过FilterInputStream和 FilterOutStream的子类,为FileOutStream添加我们所需要的功能。
2.2 FilterInputStream的各种类型
2.2.1 用于封装以字节为导向的InputStream
1) DataInputStream:从stream中读取基本类型(int、char等)数据。
2) BufferedInputStream:使用缓冲区
3) LineNumberInputStream:会记录input stream内的行数,然后可以调用getLineNumber()和setLineNumber(int)
4) PushbackInputStream:很少用到,一般用于编译器开发
2.2.2 用于封装以字符为导向的InputStream
1) 没有与DataInputStream对应的类。除非在要使用readLine()时改用BufferedReader,否则使用DataInputStream
2) BufferedReader:与BufferedInputStream对应
3) LineNumberReader:与LineNumberInputStream对应
4) PushBackReader:与PushbackInputStream对应
2.3 FilterOutStream的各种类型
2.2.3 用于封装以字节为导向的OutputStream
1) DataIOutStream:往stream中输出基本类型(int、char等)数据。
2) BufferedOutStream:使用缓冲区
3) PrintStream:产生格式化输出
2.2.4 用于封装以字符为导向的OutputStream
1) BufferedWrite:与对应
2) PrintWrite:与对应
3. RandomAccessFile
1) 可通过RandomAccessFile对象完成对文件的读写操作
2) 在产生一个对象时,可指明要打开的文件的性质:r,只读;w,只写;rw可读写
3) 可以直接跳到文件中指定的位置
4. I/O应用的一个例子
import java.io.*;
public class TestIO{
public static void main(String[] args)
throws IOException{
//1.以行为单位从一个文件读取数据
BufferedReader in =
new BufferedReader(
new FileReader("F://nepalon//TestIO.java"));
String s, s2 = new String();
while((s = in.readLine()) != null)
s2 += s + "/n";
in.close();
//1b. 接收键盘的输入
BufferedReader stdin =
new BufferedReader(
new InputStreamReader(System.in));
System.out.println("Enter a line:");
System.out.println(stdin.readLine());
//2. 从一个String对象中读取数据
StringReader in2 = new StringReader(s2);
int c;
while((c = in2.read()) != -1)
System.out.println((char)c);
in2.close();
//3. 从内存取出格式化输入
try{
DataInputStream in3 =
new DataInputStream(
new ByteArrayInputStream(s2.getBytes()));
while(true)
System.out.println((char)in3.readByte());
}
catch(EOFException e){
System.out.println("End of stream");
}
//4. 输出到文件
try{
BufferedReader in4 =
new BufferedReader(
new StringReader(s2));
PrintWriter out1 =
new PrintWriter(
new BufferedWriter(
new FileWriter("F://nepalon// TestIO.out")));
int lineCount = 1;
while((s = in4.readLine()) != null)
out1.println(lineCount++ + ":" + s);
out1.close();
in4.close();
}
catch(EOFException ex){
System.out.println("End of stream");
}
//5. 数据的存储和恢复
try{
DataOutputStream out2 =
new DataOutputStream(
new BufferedOutputStream(
new FileOutputStream("F://nepalon// Data.txt")));
out2.writeDouble(3.1415926);
out2.writeChars("/nThas was pi:writeChars/n");
out2.writeBytes("Thas was pi:writeByte/n");
out2.close();
DataInputStream in5 =
new DataInputStream(
new BufferedInputStream(
new FileInputStream("F://nepalon// Data.txt")));
BufferedReader in5br =
new BufferedReader(
new InputStreamReader(in5));
System.out.println(in5.readDouble());
System.out.println(in5br.readLine());
System.out.println(in5br.readLine());
}
catch(EOFException e){
System.out.println("End of stream");
}
//6. 通过RandomAccessFile操作文件
RandomAccessFile rf =
new RandomAccessFile("F://nepalon// rtest.dat", "rw");
for(int i=0; i<10; i++)
rf.writeDouble(i*1.414);
rf.close();
rf = new RandomAccessFile("F://nepalon// rtest.dat", "r");
for(int i=0; i<10; i++)
System.out.println("Value " + i + ":" + rf.readDouble());
rf.close();
rf = new RandomAccessFile("F://nepalon// rtest.dat", "rw");
rf.seek(5*8);
rf.writeDouble(47.0001);
rf.close();
rf = new RandomAccessFile("F://nepalon// rtest.dat", "r");
for(int i=0; i<10; i++)
System.out.println("Value " + i + ":" + rf.readDouble());
rf.close();
}
}
关于代码的解释(以区为单位):
1区中,当读取文件时,先把文件内容读到缓存中,当调用in.readLine()时,再从缓存中以字符的方式读取数据(以下简称“缓存字节读取方式”)。
1b区中,由于想以缓存字节读取方式从标准IO(键盘)中读取数据,所以要先把标准IO(System.in)转换成字符导向的stream,再进行BufferedReader封装。
2区中,要以字符的形式从一个String对象中读取数据,所以要产生一个StringReader类型的stream。
4区中,对String对象s2读取数据时,先把对象中的数据存入缓存中,再从缓冲中进行读取;对TestIO.out文件进行操作时,先把格式化后的信息输出到缓存中,再把缓存中的信息输出到文件中。
5 区中,对Data.txt文件进行输出时,是先把基本类型的数据输出屋缓存中,再把缓存中的数据输出到文件中;对文件进行读取操作时,先把文件中的数据读 取到缓存中,再从缓存中以基本类型的形式进行读取。注意in5.readDouble()这一行。因为写入第一个writeDouble(),所以为了正 确显示。也要以基本类型的形式进行读取。
6区是通过RandomAccessFile类对文件进行操作。
**************************************************************************************************
重要提示:
LineNumberInputStream,StringBufferInputStream已经废除!大家不要再用!
StringBufferInputStream,This class does not properly convert characters into bytes!
StringBufferInputStream,Deprecated. This class incorrectly assumes that bytes adequately represent characters!
**************************************************************************************************
DataInputStream流中已经没有readLine()整个方法!
替换为: BufferedReader d=new BufferedReader(new InputStreamReader(in));
--------把字节流转换为字符流接入缓存读取字符流中,再进行处理!
这个方法很大的优势!
**************************************************************************************************
-------------------------------------------------------------------
----------标准设备System.in读取数据------------------
读取字节:BufferedInputStream
读取字符:BufferedReader + InputStreamReader
----------------------------------------------
import java.io.*;
public class systemin
{
public static void main(String args[])
{ try{ //流转换!
BufferedReader is=new BufferedReader(new InputStreamReader(System.in))
String inputline=null;
while((inputline=is.readLine())!=null)
System.out.println(inputline);
is.close();
}
catch(IOException e)
{ System,out.println("IOXE: "+e);
}
}
}
----------------------------------------------------------------------------------------------
-----------------标准输出System.out是一个打印流PrintStream-----------
import java.io.*;
public class PrintStandardOutput {
public static void main(String[] args) {
String myAnswer = "No, and that's final,";
System.out.println("Hello World of Java");
System.out.println("The answer is " + myAnswer + " at this time.");
PrintWriter pw = new PrintWriter(System.out);
pw.println("The answer is " + myAnswer + " at this time.");
int i = 42;
pw.println(i + '=' + " the answer.");
pw.println("Note: " + i + '=' + " the answer.");
pw.println(i + "=" + " the answer.");
pw.println(i + ('=' + " the answer."));
pw.close();
}
}
-------------------------------------------------------------------------------------------------
-----------------------要读取(输出到—)一个文本文件-----------------------------
BufferedReader is=new BufferedReader(new FileReader("xxxx.text"));读取
BufferedOutputStream byteout=new BufferedOutputStream(new FileOutputStream("XX.dat"));
// 写出到文本!
-------------------------------------------------------------
import java.io.*;
public class OpenFileByName {
public static void main(String[] args) throws IOException {
BufferedReader is = new BufferedReader(new FileReader("myFile.txt"));
BufferedOutputStream bytesOut = new BufferedOutputStream(
new FileOutputStream("bytes.dat"));
// Code here to read from is, write to bytesOut
bytesOut.close();
}
}
-------------------------------------------------------------
import java.io.*;
public class FileIO {
private FileIO() { }
public static void copyFile(String inName, String outName)
throws FileNotFoundException, IOException {
BufferedInputStream is =
new BufferedInputStream(new FileInputStream(inName));
BufferedOutputStream os =
new BufferedOutputStream(new FileOutputStream(outName));
copyFile(is, os, true);
}
/** Copy a file from an opened InputStream to opened OutputStream */
public static void copyFile(InputStream is, OutputStream os, boolean close)
throws IOException {
int b;while ((b = is.read()) != -1) {
os.write(b);
}
is.close();
if (close)
os.close();
}
public static void copyFile(Reader is, Writer os, boolean close)
throws IOException {
int b;while ((b = is.read()) != -1) {
os.write(b);
}
is.close();
if (close)
os.close();
}
public static void copyFile(String inName, PrintWriter pw, boolean close)
throws FileNotFoundException, IOException {
BufferedReader is = new BufferedReader(new FileReader(inName));
copyFile(is, pw, close);
}
public static String readLine(String inName)
throws FileNotFoundException, IOException {
BufferedReader is = new BufferedReader(new FileReader(inName));
String line = null;
line = is.readLine();
is.close();
return line;
}
protected static final int BLKSIZ = 8192;
public void copyFileBuffered(String inName, String outName) throws
FileNotFoundException, IOException {
InputStream is = new FileInputStream(inName);
OutputStream os = new FileOutputStream(outName);
int count = 0;
byte b[] = new byte[BLKSIZ];
while ((count = is.read(b)) != -1) {
os.write(b, 0, count);
}
is.close();
os.close();
}
public static String readerToString(Reader is) throws IOException {
StringBuffer sb = new StringBuffer();
char[] b = new char[BLKSIZ];
int n;
while ((n = is.read(b)) > 0) {
sb.append(b, 0, n);
}
return sb.toString();
}
public static String inputStreamToString(InputStream is)
throws IOException {
return readerToString(new InputStreamReader(is));
}
public static void stringToFile(String text, String fileName)
throws IOException {
BufferedWriter os = new BufferedWriter(new FileWriter(fileName));
os.write(text);
os.flush();
os.close();
}
public static BufferedReader openFile(String fileName)
throws IOException {
return new BufferedReader(new FileReader(fileName));
}
}
-------------------------------------------------------------
import java,io.*;
class fileprocess
{
public static void main(String args[])
{
int b;
byte buffer[]=new byte[1000];
try
{ b=System.out.read(buffer); //存取数据,以备写出!
FileOutputStream out=new FileOotputStream("line.text");
out.write(buffer,0,b); //写出!注意字节缓冲语文件流的关系
]
catch(IOException e)
{ System.out.println(" error");
}
]
}
-------------------------------------------------------------
import java,io.*;
public class read
{
public static void main(String args[]0
{
int b;
byte buffer=new byte[2000];
try
{ FileInputStream readfile=new FileInputStream("XXXX.java");
b=readfile(buffer,0,25000);
try{String str=nre String(buffer,0,b,"Default");//构造String对象!
System.out.println(str);}
catch(UnsuportedEncodeingException e)
{ e.printStackTrace();}
catch( IOException e)
{ System.out.println(" error");}
}
}
-------------------------------------------------------------------------------------------
--------------利用 BufferedReader--FileReader读取文本文件!--------
---------------在IO中始终要注意是字节流还是字符流----------------------
--------------------------------------------------------------------------------------------
import java.io.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
class filewindow extends JFrame implements ActionListener
{
JTextArea text;
BufferedReader in;
JButton button;
FileReader file;
filewindow()
{
super("文件字符流");
Container con=getContentPane();
text=new JTextArea(50,50);
text.setBackground(Color.blue);
try{
File f=new File("E://a.txt");
file=new FileReader(f);
in=new BufferedReader(file);
/**BufferedReader(Reader in)构造函数,
*文件自字符读取流FileReader接入BufferedReader
*流中,以便用BufferedReader的对象方法readLine()高效成行读取!
*/
}
catch(FileNotFoundException e){}
catch(IOException e){}
button=new JButton("读取");
button.addActionListener(this);
con.setLayout(new BorderLayout());
setSize(300,200);
setVisible(true);
con.add(text,"Center");
con.add(button,"South");
addWindowListener(new WindowAdapter()
{public void windowClosing(WindowEvent e)
{setVisible(false);System.exit(0);}});
}
public void actionPerformed(ActionEvent e)
{
String s;
if(e.getSource()==button)
try{
while((s=in.readLine())!=null)
text.append(s+'/n');
//在这里大家还可以用BufferString来暂时保存读取的字符数据!
}
catch(IOException e1){}
}
//---------main()----------
public static void main(String args[])
{
filewindow win=new filewindow();
win.pack();
}
}
-------------------------------------------------------------------------------------------
-------------------RandomAccessFile随机读取文件---------------
import java.io.*;
public class RandomRead
{
final static String FILENAME="E://a.txt";
protected String fileName;
protected RandomAccessFile seeker;
public static void main(String[] argv) throws IOException {
RandomRead r = new RandomRead(FILENAME);
System.out.println("Offset is " + r.readOffset());
System.out.println("Message is /"" + r.readMessage() + "/".");
}
/** Constructor: save filename, construct RandomAccessFile */
public RandomRead(String fname) throws IOException {
fileName = fname;
seeker = new RandomAccessFile(fname, "rw");
}
/** Read the Offset field, defined to be at location 0 in the file. */
public int readOffset() throws IOException {
seeker.seek(0);
seeker.writeChars(FILENAME);// move to very beginning
return seeker.readInt();// and read the offset
}
/** Read the message at the given offset */
public String readMessage() throws IOException {
seeker.seek(120);// move to where
return seeker.readLine();// and read the String
}
}
- 彻底明白Java的IO系统-2
- 彻底明白Java的IO系统
- 彻底明白Java的IO系统
- 彻底明白Java的IO系统
- 彻底明白Java的IO系统
- 彻底明白Java的IO系统
- 彻底明白Java的IO系统
- 彻底明白Java的IO系统
- 彻底明白Java的IO系统
- 彻底明白Java的IO系统
- 彻底明白Java的IO系统 (转贴)
- 彻底明白Java的IO系统
- 彻底明白Java的IO系统
- 彻底明白Java的IO系统
- 彻底明白Java的IO系统 (收藏)
- 彻底明白java的IO系统
- 彻底明白Java的IO系统(转)
- 彻底明白Java的IO系统
- Picture Control装载图像
- Windows系统命令
- 缓存技术详谈
- 用POST方式获取Radio Button是否被选中的信息
- 敏捷设计的五个原则
- 彻底明白Java的IO系统
- [howto] General 5.10 - HowTo: Speed up ubuntu boot process - the way you can feel it. - updated
- ProtoType
- 13绝招教你步步高升
- 很好的页面特效总结
- FreeSWAN 结构框架
- 华为员工的命 只值一台交换机的钱 【 华为员工 胡新宇 过劳死 最新报道 】
- 常用正则表达式
- 在winXP在tomcat下配置运行jsp、servlet和ben的环境