《JAVA语言程序设计》第9章.ppt

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1、1,Java I/O操作,概念Java I/O类Java I/O操作标准输入/输出文件读写操作目录管理随机访问文件文件属性,2,概念,I/O来源控制台(console,如DOS窗口)打印/读入文件(file)读/写网络接口(TCP/UDP端口)读/写针对数据的读写以流(stream)的方式对数据进行操作,流的重要特性顺序读/写sequentially,3,概念,读/写流的一般流程读(Reading)open a stream/打开读出流while more information/判断 read information/读close the stream/关闭流写(Writing)open a

2、 stream/打开写入流while more information/判断 write information/写close the stream/关闭流,4,概念,两种流的定义(读取信息的基本数据单位)字节流(byte stream):一个字节(8-bit)一个字节读/写字符流(character stream):一个字符一个字符读/写(具有特定字符编码的数据),j a v a 语 言6A 61 76 61 D3 EF D1 D4以字节流的方式读:读8次，8个字节以字符流的方式读:读6次，6个字符,5,Java I/O操作,概念Java I/O类Java I/O操作标准输入/输出文件读写操

3、作目录管理随机访问文件文件属性,6,Java I/O类,字节流的读/写操作(来自JDK1.0)java.io.InputStream(抽象类)public abstract int read()public int read(byte b)public int read(byte b,int offset,int length)到达流的终点，无数据读出则返回-1java.io.OutputStream(抽象类)public abstract void write(int b)public void write(byte b)public void write(byte b,int offset

4、,int length)所有的读/写函数都抛出,7,Java I/O类,字符流的读/写操作(来自JDK1.1)类(抽象类)public int read()public int read(char cbuf)publc abstract int read(char cbuf,int offset,int length)到达流的终点，无数据读出则返回-1类(抽象类)public void write(int c)public void write(char cbuf)public void write(char cbuf,int offset,int length)所有的读/写函数都抛出,8,J

5、ava I/O类,I/O流的层次关系的子类class java.io.FileInputStreamclass java.io.BufferedInputStreamclass java.io.DataInputStream class java.io.ObjectInputStream,9,Java I/O类,I/O流的层次关系的子类class java.io.FileOutputStreamclass java.io.BufferedOutputStreamclass java.io.DataOutputStream,10,Java I/O类,I/O流的层次关系的子类class java.

6、io.BufferedReaderclass java.io.FilterReader class java.io.InputStreamReaderclass java.io.FileReader,11,Java I/O类,I/O流的层次关系的子类class java.io.BufferedWriterclass java.io.OutputStreamWriter class java.io.FileWriter,12,Java I/O类,I/O流的分类(12个功能类),13,Java I/O类,I/O流的分类(12个功能类),14,Java I/O类,I/O流的分类(12个功能类),15

7、,Java I/O操作,概念Java I/O类Java I/O操作标准输入/输出文件读写操作目录管理随机访问文件文件属性,16,Java I/O操作,主要内容标准输入/输出控制台屏幕打印和键盘读入文件I/O操作文件读写如何提高文件读写效率流的包装(Wrap)基本数据转换流目录管理随机访问文件(Random Access File)文件属性网络流操作(见第十三讲),17,输出:控制台屏幕打印class Test public static void main(String args)System.out.println(“Hello World!”);,标准输入/输出,C:java TestHe

8、llo World!C:,18,输入:键盘读入import java.io.IOException;class Test public static void main(String args)throws IOException byte b=new byte10;System.out.println(Received number=+System.in.read(b);,标准输入/输出,C:java TestAReceived number=3C:,19,文件读/写流程打开文件流条件判断读出/写入关闭文件流两种类型文件FileInputStream/FileOutputStream(字节流

9、)读取/生成ASCII文件FileReader/FileWriter(字符流)读取/生成包括汉字字符的文件,文件读写操作,20,文件字节流构造方法(打开字节流)利用类读取文件public FileInputStream(String name)throws FileNotFoundExceptionpublic FileInputStream(File file)throws FileNotFoundException利用类写/生成文件public FileOutputStream(String name)throws FileNotFoundExceptionpublic FileOutpu

10、tStream(String name,boolean append)throws FileNotFoundExceptionpublic FileOutputStream(File file)throws FileNotFoundExceptionpublic FileOutputStream(File file,boolean append)throws FileNotFoundException/是否向已存在的文件后添加类的构造方法public File(String pathname),文件读写操作,21,文件读写-实例1,文件读写操作,import java.io.*;public

11、class CopyBytes public static void main(String args)throws IOException File inputFile=new File(“original.txt);File outputFile=new File(“result.txt);FileInputStream in=new FileInputStream(inputFile);FileOutputStream out=new FileOutputStream(outputFile);int c;while(c=in.read()!=-1)out.write(c);in.clos

12、e();out.close();,public int read()throws IOExceptionpublic int read(byte b)throws IOExceptionpublic int read(byte b,int off,int len)throws IOException,FileInputStream in=new FileInputStream(“original.txt);FileOutputStream out=new FileOutputStream(“result.txt);,public void write(int b)throws IOExcept

13、ionpublic void write(byte b)throws IOExceptionpublic void write(byte b,int off,int len)throws IOException,打开流,读取流,写入流,关闭流,22,字符流构造方法(打开字符流)利用读取文件public FileReader(String fileName)throws FileNotFoundExceptionpublic FileReader(File file)throws FileNotFoundException利用写/生成文件public FileWriter(String file

14、Name)throws IOExceptionpublic FileWriter(String fileName,boolean append)throws IOExceptionpublic FileWriter(File file)throws IOExceptionpublic FileWriter(File file,boolean append)throws IOException类的构造方法public File(String pathname),文件读写操作,23,文件读写-实例2,文件读写操作,import java.io.*;public class Copy public

15、static void main(String args)throws IOException File inputFile=new File(“original.txt);File outputFile=new File(“result.txt);FileReader in=new FileReader(inputFile);FileWriter out=new FileWriter(outputFile);int c;while(c=in.read()!=-1)out.write(c);in.close();out.close();,FileReader in=new FileReader

16、(“original.txt);FileWriter out=new FileWriter(“result.txt);,public int read()throws IOExceptionpublic int read(char cbuf)throws IOExceptionpublic int read(char cbuf,int off,int len)throws IOException,public void write(int b)throws IOExceptionpublic void write(char cbuf)throws IOExceptionpublic void

17、write(char cbuf,int off,int len)throws IOException,打开流,读取流,写入流,关闭流,24,两类缓冲流针对字节流java.io.BufferedInputStream类java.io.BufferedOutputStream类针对字符流java.io.BufferedReader类java.io.BufferedWriter类,如何提高文件读写效率,25,构造方法类public BufferedInputStream(InputStream in)默认缓冲字节(2048 bytes)public BufferedInputStream(Input

18、Stream in,int size)public BufferedOutputStream(OutputStream out)默认缓冲字节(512 bytes)public BufferedOutputStream(OutputStream out,int size)类public BufferedReader(Reader in)默认缓冲字节(8192 bytes)public BufferedReader(Reader in,int sz)public BufferedWriter(Writer out)默认缓冲字节(8192 byte)public BufferedWriter(Wri

19、ter out,int sz),如何提高文件读写效率,26,String filename=“test.txt”;FileInputStream fis=new FileInputStream(filename);int count=0;int c;while(c=fis.read()!=-1)if(c=A)count+;fis.close();System.out.println(count);,实例1(判断一个文本文件包含多少个字符A),如何提高文件读写效率,普通的文件流,27,如何提高文件读写效率,String filename=“test.txt”;FileInputStream fi

20、s=new FileInputStream(filename);BufferedInputStream bis=new BufferedInputStream(fis);int count=0;int c;while(c=bis.read()!=-1)if(c=A)count+;fis.close();System.out.println(count);,利用缓冲流,实例1(判断一个文本文件包含多少个字符A),28,如何提高文件读写效率,FileInputStream fis=new FileInputStream(“test.txt”);int count=0;final int BUFSI

21、ZE=1024;byte buf=new byteBUFSIZE;int len;while(len=fis.read(buf)!=-1)for(int i=0;i len;i+)if(bufi=A)count+;fis.close();,自定义一个缓冲区,实例1(判断一个文本文件包含多少个字符A),29,String filename=“test.txt”;FileReader fr=new FileReader(filename);BufferedReader br=new BufferedReader(fr);int count=0;while(br.readLine()!=null)c

22、ount+;br.close();System.out.println(count);,实例2(按行读取数据),如何提高文件读写效率,30,概述,流的包装(wrap),FileReader fr=new FileReader(filename);BufferedReader br=new BufferedReader(fr);,String filename=“test.txt”;BufferedReader br=new BufferedReader(new FileReader(filename);,PrintWriter out=new PrintWriter(new BufferedW

23、riter(new FileWriter(filename);,public String readLine()in java.io.BufferedReader 按行读数据public void println(String x)in java.io.PrintWriter 按行打印数据,利用不同流的特点(方法)寻找合适的方法完成特定的需求对已有的流进行再处理,31,流的种类节点流直接对数据源进行读/写操作的流处理流对一个已有的流进行某种操作(进行加工)的流,流的包装(wrap),32,节点流FileInputStream,PipedInputStream,ByteArrayInputStr

24、eam,StringBufferInputStreamFileOutputStream,PipedOutputStream,ByteArrayOutputStreamCharArrayReader,FileReader,PipedReader,StringReaderCharArrayWriter,FileWriter,PipedWriter,StringWriter,流的包装(wrap),33,处理流FilterOutputStream,DataOutputStream,BufferedOutputStream,PrintStreamFilterInputStream,LineNumberI

25、nputStream,DataInputStream,BufferedInputStream,PushbackInputStreamBufferedReader,LineNumberReader,InputStreamReader,FilterReader,PushBackReaderBufferedWriter,OutputStreamReader,FilterWriter,PrintWriter,流的包装(wrap),34,一个实例类public FileReader(File file)throws FileNotFoundExceptionpublic FileReader(Strin

26、g fileName)throws FileNotFoundException类public BufferedReader(Reader in)默认缓冲字节(8192 bytes)public BufferedReader(Reader in,int sz)流的包装改变了流的行为,流的包装(wrap),35,实例1(在DOS屏幕上实现回显功能),流的包装(wrap),import java.io.*;public class Echo public static void main(String args)throws IOException BufferedReader in=new Buf

27、feredReader(new InputStreamReader(System.in);String s;while(s=in.readLine().length()!=0)System.out.println(s);,public static final InputStream in 类)public InputStreamReader(InputStream in)类)public BufferedReader(Reader in)类),D:java EchoHelloHelloTestTest D:,36,概述类读取基本类型的数据public DataInputStream(Inpu

28、tStream in)public final boolean readBoolean()public final byte readByte()public final char readChar()public final int readInt()类写基本类型的数据public DataOutputStream(OutputStream out)public final void writeBoolean(boolean v)public final void writeByte(int v)public final void writeChar(int v)public final v

29、oid writeInt(int v),基本数据转换流,处理流,处理流,37,DataOutputStream out=new DataOutputStream(new FileOutputStream(invoice.txt);double prices=19.99,9.99;int units=12,8;String descs=Java T-shirt,Java Mug;for(int i=0;i prices.length;i+)out.writeDouble(pricesi);out.writeChar(t);out.writeInt(unitsi);out.writeChar(t)

30、;out.writeChars(descsi);out.writeChar(n);out.close();,实例1(写基本类型的数据),基本数据转换流,19.99 12 Java T-shirt9.99 8 Java Bag,38,基本数据转换流-实例,基本数据转换流,DataInputStream in=new DataInputStream(new FileInputStream(invoice.txt);double total;try while(true)double price=in.readDouble();in.readChar();int unit=in.readInt();

31、in.readChar();char chr;StringBuffer desc=new StringBuffer(20);while(chr=in.readChar()!=n)desc.append(chr);System.out.println(price+“+unit+“+desc);total=total+unit*price;catch(EOFException e)System.out.println(total);in.close();,19.99 12 Java T-shirt9.99 8 Java Bag 599.68,invoice.txt19.99 12 Java T-s

32、hirt9.99 8 Java Bag,39,概述类表示文件和目录的路径名构造方法public File(String pathname)public File(String parent,String child)public File(File parent,String child)parent通常表示一个目录，child则表示一个目录或文件路径名(pathname)UNIX平台上绝对路径的前缀“/”，相对路径无前缀，例“/etc/inetd.conf”、“inetd.conf”Windows平台，绝对路径名的前缀由“盘符:”组成；UNC 路径名前缀为“”，然后是主机名和共享名，相对路径

33、名无盘符，例“c:windowsnotepad.exe”、“notepad.exe”,目录管理,40,方法public boolean canWrite()/canRead()public boolean exists()public boolean delete()删除文件或目录，若删除目录，要求该目录必须为空public boolean createNewFile()创建一个空文件，当且仅当该文件不存在public boolean isDirectory()/isFile()/isHidden()public long lastModified()/public boolean setLa

34、stModified(long time)public String list()得到当前目录下的所有文件名和目录名，若该File对象不是表示目录，则返回nullpublic boolean mkdir()/mkdirs()创建一个目录public boolean renameTo(File dest)public boolean setReadOnly(),目录管理,41,目录管理方法举例,目录管理,import java.io.File;public class DirList public static void main(String args)File path=new File(.

35、);String list=path.list();for(int i=0;i list.length;i+)System.out.println(listi);,42,随机访问文件(Random Access File)类读写操作在同一个类中完成，须在构造对象时指定参数通过移动文件指针(file pointer)在文件的指定位置进行读写操作构造方法public RandomAccessFile(String name,String mode)throws FileNotFoundExceptionpublic RandomAccessFile(File file,String mode)th

36、rows FileNotFoundExceptionmode:“r”,“rw”,随机访问文件,43,方法public void seek(long pos)设定文件指针public int read()public int read(byte b)public int read(byte b,int off,int len)public final boolean readBoolean()/readByte()/readChar()/readShort()/readInt()/readDouble()/readFloat()public final String readLine()publ

37、ic void write(int b)public void write(byte b)public void write(byte b,int off,int len)public final void writeBoolean()/writeByte()/writeChar()/writeShort()/writeInt()/writeDouble()/writeFloat(),随机访问文件,44,随机访问文件(Random Access File)-实例,随机访问文件,RandomAccessFile rf=new RandomAccessFile(rtest.dat,rw);for(

38、int i=0;i 10;i+)rf.writeDouble(i*1.414);rf.close();rf=new RandomAccessFile(rtest.dat,rw);rf.seek(5*8);rf.writeDouble(47.0001);rf.close();rf=new RandomAccessFile(rtest.dat,r);for(int i=0;i 10;i+)System.out.println(Value+i+:+rf.readDouble();rf.close();,运行结果:Value 0:0.0Value 1:1.414Value 2:2.828Value 3

39、:4.242Value 4:5.656Value 5:47.0001Value 6:8.484Value 7:9.898Value 8:11.312Value 9:12.725999999999999,45,文件属性读和写的权限文件长度修改时间是否是目录类设定文件属性查询文件属性,文件属性,46,文件属性,获取文件路径,import java.io.*;class AttrDemo1 public static void main(String args)throws IOException File testfile=new File(.+File.separatorChar+test.tx

40、t);testfile.createNewFile();System.out.println(name=+testfile.getName();System.out.println(path=+testfile.getPath();System.out.println(absolute path=+testfile.getAbsolutePath();System.out.println(canonical path=+testfile.getCanonicalPath();,类public static final char separatorCharUNIX系统为/，WINDOWS系统为,

41、D:javajava AttrDemo1name=test.txtpath=.test.txtabsolute path=D:java.test.txtcanonical path=D:javatest.txt,47,文件属性,获取文件修改时间,import java.io.*;import java.util.Date;public class AttrDemo2 public static void main(String args)throws IOException File testfile=new File(test.txt);testfile.delete();testfile.

42、createNewFile();long modtime=testfile.lastModified();System.out.println(last modification time#1=+new Date(modtime);testfile.setLastModified(0);modtime=testfile.lastModified();System.out.println(last modification time#2=+new Date(modtime);,D:javajava AttrDemo2last modification time#1=Wed Mar 17 10:3

43、3:11 CST 2004last modification time#2=Thu Jan 01 08:00:00 CST 1970,48,文件属性,获取和设定文件长度,import java.io.*;public class AttrDemo3 public static void main(String args)throws IOException File testfile=new File(test.txt);testfile.delete();testfile.createNewFile();System.out.println(length#1=+testfile.length

44、();RandomAccessFile raf=new RandomAccessFile(test.txt,rw);raf.setLength(100);raf.close();System.out.println(length#2=+testfile.length();,D:javajava AttrDemo3length#1=0length#2=100,49,文件属性,设置读写权限,import java.io.*;public class AttrDemo4 public static void main(String args)throws IOException File testf

45、ile=new File(test.txt);testfile.delete();testfile.createNewFile();if(testfile.canRead()System.out.println(file can be read#1);if(testfile.canWrite()System.out.println(file can be written#1);testfile.setReadOnly();if(testfile.canRead()System.out.println(file can be read#2);if(testfile.canWrite()System.out.println(file can be written#2);,D:javajava AttrDemo4file can be read#1file can be written#1file can be read#2,