IO简单示例

File[/b]类[/b][/b]

用于对磁盘上的文件或目录进行操作

直接父类是Object

创建一个文件

public class FileTest { public static void main(String[] args) throws IOException { File file = new File("C:/text.txt"); System.out.println(file.createNewFile()); } }

在一个目录下创建文件

public class FileTest2 { public static void main(String[] args) throws IOException { File file = new File("C:/abc"); File file2 = new File(file,"hello.txt"); System.out.println(file2.createNewFile()); File file3 = new File(file,"xyz/world.txt"); System.out.println(file3.createNewFile()); } }

创建目录操作

public class FileTest3 { public static void main(String[] args) { File file = new File("C:/abc/xyz/hello"); System.out.println(file.mkdirs()); System.out.println(file.isDirectory()); } }

列出指定目录下的文件或目录

public class FileTest4 { public static void main(String[] args) { File file = new File("C:/java"); String[] names = file.list(); for(String name: names) { System.out.println(name); } File[] files = file.listFiles(); for(File f : files) { System.out.println(f.getName()); System.out.println(f.getParent()); } } }

文件删除操作

public class FileTest5 { public static void main(String[] args) throws IOException { File file = new File("C:/abc/xyz/hello/text.txt"); //file.createNewFile(); boolean delete = file.delete(); System.out.println(delete); } }

文件名过滤操作

public class FileTest6 { public static void main(String[] args) { File file = new File("C:/java"); /*String[] names = file.list(); for(String name : names) { if(name.endsWith(".java")) { System.out.println(name); } }*/ String[] names = file.list(new FilenameFilter() { @Override public boolean accept(File dir, String name) { if(name.endsWith(".java")) { return true; } return false; } }); for(String name : names ) { System.out.println(name); } } }

文件分隔符的使用

public class FileTest7 { public static void main(String[] args) throws IOException { //不加盘符表示java安装的默认盘 File file = new File(File.separator + "helo.txt"); System.out.println(file.createNewFile()); } }

递归的使用（关键在于要先指定一个出口，才不会出现死循环）

public class Test1 { public static int calc(int num) { if(num ==1 ) return 1; else return num * calc(num - 1); } public static void main(String[] args) { System.out.println(calc(5)); } }

斐波那契数列

public class Fabonaci { public int calc(int pos) { if(1 == pos || 2 == pos) return 1; else return calc(pos-1)+calc(pos-2); } private void sysout() { Fabonaci fab = new Fabonaci(); fab.calc(30); } }

删除指定目录下的所有文件（用递归实现）

public class FileTest8 { public static void deleteAll(File file) { if(file.isFile() || 0 == file.list().length) { file.delete(); } else { File[] files = file.listFiles(); for(File f : files) { deleteAll(f); f.delete(); } } } public static void main(String[] args) { File file = new File("C:/test"); try { deleteAll(file); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } }

把指定目录下的文件结构以树的形式打印出来

public class FileTest9 { // 判断目录或文件所在的层数 private static int times; // 把目录下的文件以树结构的形式打印出来。 static void treeShow(File file) { if (file.isFile() || 0 == file.listFiles().length) { return; } else { File[] files = file.listFiles(); files = sortFile(files); for (File f : files) { StringBuffer sb = new StringBuffer(); if (f.isDirectory()) { sb.append(getTAbs(times)); sb.append(f.getName()); sb.append("\\"); } else { sb.append(getTAbs(times)); sb.append(f.getName()); } System.out.println(sb); if (f.isDirectory()) { times++; treeShow(f); times--; } } } } // 取得每个目录或文件所处层数的缩进 private static String getTAbs(int times) { StringBuffer sb = new StringBuffer(); for (int i = 0; i < times; i++) { sb.append("\t"); } return sb.toString(); } // 把目录下所有文件以目录为先的次序排序 private static File[] sortFile(File[] files) { List<File> list = new ArrayList<File>(); for (File f : files) { if (f.isDirectory()) { list.add(f); } } for (File f : files) { if (f.isFile()) { list.add(f); } } return list.toArray(new File[files.length]); } public static void main(String[] args) { File file = new File("C:/xdict"); treeShow(file); } }

Stream[/b]类[/b][/b]

从功能上分：输入流（InputStream）和输出流（OutputStream）

从结构上分：字节流(Byte
Streams)和字符流(Character
Streams)

字节流输入输出的基础是抽象类InputStream和OutputStream

字符流输入输出的基础是抽象类Reader和Writer

流的分类：

节点流：从特定的地方读写的流类。

过滤流：使用节点流作为输入或输出。过滤流是使用一个已存在的输入流或输出流连接创建的。

字节流的使用[/b]

FileInputStream类的使用

public class InputStreamTest { public static void main(String[] args) throws Exception { InputStream is = new FileInputStream("c:/hello.txt"); byte[] buffer = new byte[200]; int length = 0; if (-1 != (length = is.read(buffer, 0, 200))) { String str = new String(buffer, 0, length); System.out.println(str); } is.close(); } }

FileOutputStream类的使用

public class OutputStreamTest { public static void main(String[] args) throws IOException { OutputStream os = new FileOutputStream("c:/out.txt",true); String str = "\nwelcomle"; byte[] buffer = str.getBytes(); os.write(buffer); os.close(); } }

BufferedInputStream类，继承自FilterInputStream

BufferedOutputStream类，继承自FilterOutputStream

public class BufferedOutputStreamTest { public static void main(String[] args) throws Exception { OutputStream os = new FileOutputStream("1.txt"); BufferedOutputStream bos = new BufferedOutputStream(os); bos.write("http://www.sina.com.cn".getBytes()); bos.close(); os.close(); } }

ByteArrayInputStream类

public class ByteArrayInputStreamTest { public static void main(String[] args) throws Exception { String str = "abcdef"; byte[] byteArr = str.getBytes(); ByteArrayInputStream bais = new ByteArrayInputStream(byteArr); int c; //一次只读一个字符 while(-1 != (c = bais.read())) { if(0==c) { System.out.println((char)c); } else { System.out.println(Character.toUpperCase((char) c)); } } bais.close(); } }

ByteArrayOutputStream类

public class ByteArrayOutputStreamTest { public static void main(String[] args) throws Exception { String str = "hello world welcome"; byte[] arr = str.getBytes(); ByteArrayOutputStream baos = new ByteArrayOutputStream(); //把字节数组写入到字节数组输出流中 baos.write(arr); //从字节数组输出流中得到字节数组 byte[] result = baos.toByteArray(); for(byte b : result) { System.out.println((char)b); } OutputStream os = new FileOutputStream("c:/test.txt"); //把字节数组写入到文件中。 baos.writeTo(os); baos.close(); os.close(); } }

DataInputStream类，继承自FilterInputStream

DataOutputStream类，继承自FilterOutputStream

public class DataOutputStreamTest { public static void main(String[] args) throws Exception { DataOutputStream dos = new DataOutputStream(new BufferedOutputStream(new FileOutputStream("data.txt"))); byte b = 3; int i = 12; char c = 'c'; float f = 0.3f; dos.writeByte(b); dos.writeInt(i); dos.writeChar(c); dos.writeFloat(f); dos.close(); DataInputStream dis = new DataInputStream(new BufferedInputStream(new FileInputStream("data.txt"))); System.out.println(dis.readByte()); System.out.println(dis.readInt()); System.out.println(dis.readChar()); System.out.println(dis.readFloat()); dis.close(); } }

自定义一个ByteArrayInputStream

public class MyOwnStream { public static void main(String[] args) throws Exception { byte[] bytes = new byte[16]; for (int i = 0; i < bytes.length; i++) { bytes = (byte) i; } MyInputStream myis = new MyInputStream(bytes); int c = 0; while (true) { if (-1 == (c = myis.read())) { break; } System.[i]out.print(c + " "); } myis.close(); } } // 这里使用了装饰者模式 class MyInputStream extends InputStream { protected byte[] buffer; protected int ptr = 0; public MyInputStream(byte[] bytes) { buffer = bytes; } @Override public int read() throws IOException { return (ptr < buffer.length) ? buffer[ptr++] : -1; } }

重写InputStream类方法完整的例子

public class MyOwnStream2 extends InputStream { protected byte[] data; protected int ptr = 0; protected int mark = 0; public MyOwnStream2(byte[] bytes) { this.data = bytes; } @Override public int read() throws IOException { return (ptr < data.length) ? data[ptr++] : -1; } @Override public int read(byte[] b, int off, int len) throws IOException { if (ptr > data.length || len < 0) { return -1; } if ((ptr + len) > data.length) { len = data.length - ptr; } if (0 == len) { return 0; } System.arraycopy(data, ptr, b, off, len); ptr += len; return len; } @Override public long skip(long n) throws IOException { return super.skip(n); } @Override public int available() throws IOException { return data.length - ptr; } @Override public void close() throws IOException { ptr = data.length; } @Override public synchronized void mark(int readlimit) { this.mark = readlimit; } @Override public synchronized void reset() throws IOException { if (mark > 0 || mark < data.length) { throw new IOException("The position is invalid."); } ptr = mark; } @Override public boolean markSupported() { return true; } }

字符流的使用[/b]

InputStreamReader

OutputStreamWrite

public class StreamTest { public static void main(String[] args) throws Exception { FileOutputStream fos = new FileOutputStream("file.txt"); OutputStreamWriter osw = new OutputStreamWriter(fos); BufferedWriter bw = new BufferedWriter(osw); bw.write("http://www.google.com"); bw.write("\n"); bw.write("http://www.baidu.com"); bw.close(); FileInputStream fis = new FileInputStream("file.txt"); InputStreamReader isr = new InputStreamReader(fis); BufferedReader br = new BufferedReader(isr); /*System.out.println(br.readLine()); System.out.println(br.readLine()); System.out.println(br.readLine());*/ String str = br.readLine(); while(null != str) { System.out.println(str); str = br.readLine(); } br.close(); } }

BufferedReader

public class StreamTest2 { public static void main(String[] args) throws Exception { InputStreamReader isr = new InputStreamReader(System.in); BufferedReader br = new BufferedReader(isr); String str; while(null != (str = br.readLine())) { System.out.println(str); } br.close(); } }

BufferedWrite

FileOutputStream fos = new FileOutputStream("file.txt"); OutputStreamWriter osw = new OutputStreamWriter(fos); BufferedWriter bw = new BufferedWriter(osw); bw.write("http://www.google.com"); bw.write("\n"); bw.write("http://www.baidu.com"); bw.close();

FileReader

public class FileReaderTest { public static void main(String[] args) throws Exception { FileReader fr = new FileReader("src/com/anllin/io3/FileReaderTest.java"); BufferedReader br = new BufferedReader(fr); String str ; while(null != (str = br.readLine())) { System.out.println(str); } br.close(); } }

FileWriter

public class FileWriteTest { public static void main(String[] args) throws Exception { String str = "hello world welcome nice bueaty"; char[] buffer = new char[str.length()]; str.getChars(0,str.length(),buffer,0); FileWriter fr = new FileWriter("file2.txt"); fr.write(buffer); fr.close(); } }

CharArrayReader

public class CharArrayReaderTest { public static void main(String[] args) throws Exception { String str = "abcdefghijklmnopqrstuvwxyz"; char[] buffer = new char[str.length()]; str.getChars(0, str.length(),buffer,0); CharArrayReader car = new CharArrayReader(buffer); int i ; while(-1 != (i = car.read())) { System.out.println((char)i); } car.close(); } }

字符集的分类：

ASCII
GB2312 GBK Unicode iso-8859- 1 UTF-8

public class CharsetTest { public static void main(String[] args) { SortedMap<String,Charset> map = Charset.availableCharsets(); Set<String> set = map.keySet(); for(Iterator<String> iter = set.iterator(); iter.hasNext();) { System.out.println(iter.next()); } } }

RandomAccessFile类，可以随机对文件进行读写操作。

public class RandomAccessFileTest { public static void main(String[] args) throws Exception { Person p = new Person(1, "anllin", 170); RandomAccessFile raf = new RandomAccessFile("person.txt", "rw"); p.write(raf); raf.seek(0);//让读的位置回到文件的开头 Person p2 = new Person(); p2.read(raf); System.out.println(p2.getId() + ", " + p2.getName() + ", " + p2.getHeight()); } } class Person { int id; String name; double height; public Person() { } public Person(int id, String name, double height) { this.id = id; this.name = name; this.height = height; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public double getHeight() { return height; } public void setHeight(double height) { this.height = height; } public void write(RandomAccessFile raf) throws Exception { raf.writeInt(id); raf.writeUTF(name); raf.writeDouble(height); } public void read(RandomAccessFile raf) throws Exception { this.id = raf.readInt(); this.name = raf.readUTF(); this.height = raf.readDouble(); } }