JAVA语言程序设计》第9章.ppt

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 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-1 java.io.OutputStream (抽象类) public abstract void write(int b) public void write(byte b) public void write(byte b, int offset, int length) 所有的读/写函数都抛出java.io.IOException,7,Java I/O类,字符流的读/写操作(来自JDK1.1) java.io.Reader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 java.io.Writer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java.io.IOException,8,Java I/O类,I/O流的层次关系 class java.io.InputStream的子类 class java.io.ByteArrayInputStream class java.io.FileInputStream class java.io.FilterInputStream class java.io.BufferedInputStream class java.io.DataInputStream class java.io.LineNumberInputStream class java.io.PushbackInputStream class java.io.ObjectInputStream class java.io.PipedInputStream class java.io.SequenceInputStream class java.io.StringBufferInputStream ,9,Java I/O类,I/O流的层次关系 class java.io.OutputStream的子类 class java.io.ByteArrayOutputStream class java.io.FileOutputStream class java.io.FilterOutputStream class java.io.BufferedOutputStream class java.io.DataOutputStream class java.io.PrintStream class java.io.ObjectOutputStream class java.io.PipedOutputStream ,10,Java I/O类,I/O流的层次关系 class java.io.Reader的子类 class java.io.BufferedReader class java.io.LineNumberReader class java.io.CharArrayReader class java.io.FilterReader class java.io.PushbackReader class java.io.InputStreamReader class java.io.FileReader class java.io.PipedReader class java.io.StringReader ,11,Java I/O类,I/O流的层次关系 class java.io.Writer的子类 class java.io.BufferedWriter class java.io.CharArrayWriter class java.io.FilterWriter class java.io.OutputStreamWriter class java.io.FileWriter class java.io.PipedWriter class java.io.PrintWriter class java.io.StringWriter ,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,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 Test Hello 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 Test A Received number=3 C:,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) 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java.io.FileInputStream类读取文件 public FileInputStream(String name) throws FileNotFoundException public FileInputStream(File file) throws FileNotFoundException 利用java.io.FileOutputStream类写/生成文件 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 /是否向已存在的文件后添加 java.io.File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 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.close(); out.close(); ,public int read () throws IOException public int read (byte b) throws IOException public 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 IOException public void write (byte b) throws IOException public 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java.io.FileReader读取文件 public FileReader(String fileName) throws FileNotFoundException public FileReader(File file) throws FileNotFoundException 利用java.io.FileWriter写/生成文件 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 java.io.File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 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(“original.txt“); FileWriter out = new FileWriter(“result.txt“);,public int read () throws IOException public int read (char cbuf) throws IOException public int read (char cbuf, int off, int len) throws IOException,public void write (int b) throws IOException public void write (char cbuf) throws IOException public void 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 java.io.BufferedInputStream类 public BufferedInputStream(InputStream in) 默认缓冲字节(2048 bytes) public BufferedInputStream(InputStream in, int size) public BufferedOutputStream(OutputStream out) 默认缓冲字节(512 bytes) public BufferedOutputStream(OutputStream out, int size) java.io.BufferedReader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(Writer 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 fis = 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 BUFSIZE = 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) count+; 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 BufferedWriter ( 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, ByteArrayInputStream, StringBufferInputStream FileOutputStream, PipedOutputStream, ByteArrayOutputStream CharArrayReader, FileReader, PipedReader, StringReader CharArrayWriter, FileWriter, PipedWriter, StringWriter,流的包装(wrap),33,处理流 FilterOutputStream, DataOutputStream, BufferedOutputStream, PrintStream FilterInputStream, LineNumberInputStream, DataInputStream, BufferedInputStream, PushbackInputStream BufferedReader, LineNumberReader, InputStreamReader, FilterReader, PushBackReader BufferedWriter, OutputStreamReader, FilterWriter, PrintWriter,流的包装(wrap),34,一个实例 java.io.FileReader类 public FileReader(File file) throws FileNotFoundException public FileReader(String fileName) throws FileNotFoundException java.io.BufferedReader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 BufferedReader( new InputStreamReader(System.in); String s; while(s = in.readLine().length() != 0) System.out.println(s); ,public static final InputStream in (java.lang.System类) public InputStreamReader(InputStream in) (java.io.InputStreamReader类) public BufferedReader(Reader in) (java.io.BufferedReader类),D:java Echo Hello Hello Test Test D:,36,概述 java.io.DataInputStream类读取基本类型的数据 public DataInputStream(InputStream in) public final boolean readBoolean() public final byte readByte() public final char readChar() public final int readInt() java.io.DataOutputStream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 void 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); 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-shirt 9.99 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(); 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-shirt 9.99 8 Java Bag 599.68,invoice.txt 19.99 12 Java T-shirt 9.99 8 Java Bag,39,概述 java.io.File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 setLastModified(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null public 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(“.“); 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) java.io.RandomAccessFile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 FileNotFoundException public RandomAccessFile(File file, String mode) throws FileNotFoundException mode: “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() public 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(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: 0.0 Value 1: 1.414 Value 2: 2.828 Value 3: 4.242 Value 4: 5.656 Value 5: 47.0001 Value 6: 8.484 Value 7: 9.898 Value 8: 11.312 Value 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 java.io.File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.txt“); 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(); ,java.io.File类 public static final char separatorChar UNIX系统为/，WINDOWS系统为,D:javajava AttrDemo1 name=test.txt path=.test.txt absolute path = D:java.test.txt canonical path = D:javatest.txt,47,文件属性,获取文件修改时间,import java.io.*; import java.util.Date; p