import java.io.File;
import java.io.IOException;
import java.text.DateFormat;
import java.util.Date;  public class FileMethodDemo {  /** * @param args * @throws IOException */  public static void main(String[] args) throws IOException {  // getDemo();  // createAndDeleteDemo();  // isDemo();  // renameToDemo();  // listRootsDemo();
    }  public static void listRootsDemo() {  File[] files = File.listRoots();  for (File file : files) {  System.out.println(file);  }  File file = new File("c:\\");  System.out.println(file.getFreeSpace());  System.out.println(file.getTotalSpace());  System.out.println(file.getUsableSpace());  }  public static void renameToDemo() {  File f1 = new File("c:\\0.mp3");  File f2 = new File("d:\\9.mp3");  f1.renameTo(f2);  }  public static void isDemo() throws IOException {  File f = new File("a.txt");  boolean b = f.exists();  System.out.println("exists?:" + b);  // 最好先判断是否存在  System.out.println("isFile?:" + f.isFile());  System.out.println("isDirectory?:" + f.isDirectory());  }  public static void createAndDeleteDemo() throws IOException {  File dir = new File("abc\\a\\b\\c\\d");  // boolean b=dir.mkdir();//创建单级目录  // boolean b=dir.mkdirs();//创建多级目录  // System.out.println("b:"+b);  System.out.println("del:" + dir.delete());  // 文件的创建和删除  File file = new File("file.txt");  /* * 和输出流不一样，如果文件不存在，则创建；如果文件存在，则不创建。 */  // boolean b=file.createNewFile();  // System.out.println("b:"+b);  // boolean b=file.delete();  // System.out.println("b:"+b);
    }  public static void getDemo() {  File file = new File("a.txt");  String name = file.getName();  String abspath = file.getAbsolutePath();  String path = file.getPath();  long len = file.length();  long time = file.lastModified();  Date date = new Date(time);  DateFormat dateFormat = DateFormat.getDateTimeInstance(DateFormat.LONG,  DateFormat.LONG);  String str_time = dateFormat.format(date);  System.out.println("parent:" + file.getParent());// 文件对象中是绝对路径时，获取父目录；相对路径时，null
  System.out.println("name：" + name);  System.out.println("path：" + path);  System.out.println("abspath：" + abspath);  System.out.println("len:" + len);  System.out.println("time：" + time);  System.out.println("str_time:" + str_time);  }
}  

import java.io.*;
import java.util.*;class PropertiesDemo
{public static void main(String[] args) throws IOException{//method_1();
        loadDemo();}public static void loadDemo()throws IOException{Properties prop = new Properties();FileInputStream fis = new FileInputStream("info.txt"); //源文件//将流中的数据加载进集合。prop.load(fis);        //从输入流中读取属性列表（键和元素对）。
prop.setProperty("wangwu","39");FileOutputStream fos = new FileOutputStream("info.txt");prop.store(fos,"haha");//    System.out.println(prop);
        prop.list(System.out);fos.close();fis.close();}//演示，如何将流中的数据存储到集合中。//想要将info.txt中键值数据存到集合中进行操作。/*1,用一个流和info.txt文件关联。2，读取一行数据，将该行数据用"="进行切割。3，等号左边作为键，右边作为值。存入到Properties集合中即可。*/public static void method_1()throws IOException{BufferedReader bufr = new BufferedReader(new FileReader("info.txt"));String line = null;Properties prop = new Properties();while((line=bufr.readLine())!=null){String[] arr = line.split("=");///System.out.println(arr[0]+"...."+arr[1]);prop.setProperty(arr[0],arr[1]);}bufr.close();System.out.println(prop);}//    设置和获取元素。public static void setAndGet(){Properties prop = new Properties();prop.setProperty("zhangsan","30");prop.setProperty("lisi","39");//        System.out.println(prop);String value = prop.getProperty("lisi");//System.out.println(value);
            prop.setProperty("lisi",89+"");Set<String> names = prop.stringPropertyNames(); for(String s : names)                          {System.out.println(s+":"+prop.getProperty(s));}}
}

import java.io.*;
import java.util.*;
class SequenceDemo
{public static void main(String[] args) throws IOException{Vector<FileInputStream> v = new Vector<FileInputStream>();v.add(new FileInputStream("c:\\1.txt"));v.add(new FileInputStream("c:\\2.txt"));v.add(new FileInputStream("c:\\3.txt"));Enumeration<FileInputStream> en = v.elements();SequenceInputStream sis = new SequenceInputStream(en);FileOutputStream fos = new FileOutputStream("c:\\4.txt");byte[] buf = new byte[1024];int len =0;while((len=sis.read(buf))!=-1){fos.write(buf,0,len);}fos.close();sis.close();}
}===================================================================
对象的持久化（序列化）ObjectOutputStreamimport java.io.*;class ObjectStreamDemo
{public static void main(String[] args) throws Exception{//writeObj();
        readObj();}public static void readObj()throws Exception{ObjectInputStream ois = new ObjectInputStream(new FileInputStream("obj.txt"));Person p = (Person)ois.readObject();System.out.println(p);ois.close();}public static void writeObj()throws IOException{ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("obj.txt"));oos.writeObject(new Person("lisi0",399,"kr"));oos.close();}
}被传送的类必须是被序列化的，序列号由成员变量生成，类修改之后序列号改变。import java.io.*;
class Person implements Serializable   //启用Serializable实现其序列化
{public static final long serialVersionUID = 42L; //自己指定uid，也可以省略有系统生成private String name;transient int age;    //如果用transient声明一个实例变量，当对象存储时，它的值不需要维持。也就是不能被序列化。static String country = "cn";    //    静态变量不能被序列化。（只序列化堆中的变量）Person(String name,int age,String country){this.name = name;this.age = age;this.country = country;}public String toString(){return name+":"+age+":"+country;}
}

import java.io.*;class Read implements Runnable
{private PipedInputStream in;Read(PipedInputStream in){this.in = in;}public void run(){try{byte[] buf = new byte[1024];System.out.println("读取前。。没有数据阻塞");int len = in.read(buf);    //阻塞式方法System.out.println("读到数据。。阻塞结束");String s= new String(buf,0,len);System.out.println(s);in.close();}catch (IOException e){throw new RuntimeException("管道读取流失败");}}
}class Write implements Runnable
{private PipedOutputStream out;Write(PipedOutputStream out){this.out = out;}public void run(){try{System.out.println("开始写入数据，等待6秒后。");Thread.sleep(6000);out.write("piped lai la".getBytes());out.close();}catch (Exception e){throw new RuntimeException("管道输出流失败");}}
}class  PipedStreamDemo
{public static void main(String[] args) throws IOException{PipedInputStream in = new PipedInputStream();PipedOutputStream out = new PipedOutputStream();in.connect(out);Read r = new Read(in);Write w = new Write(out);new Thread(r).start();new Thread(w).start();}
}

import java.io.*;class RandomAccessFileDemo
{public static void main(String[] args) throws IOException{//writeFile_2();//readFile();//System.out.println(Integer.toBinaryString(258));
}public static void readFile()throws IOException{RandomAccessFile raf = new RandomAccessFile("ran.txt","r");//调整对象中指针。//raf.seek(8*1);//跳过指定的字节数raf.skipBytes(8);byte[] buf = new byte[4];raf.read(buf);String name = new String(buf);int age = raf.readInt();System.out.println("name="+name);System.out.println("age="+age);raf.close();}public static void writeFile_2()throws IOException{RandomAccessFile raf = new RandomAccessFile("ran.txt","rw");raf.seek(8*0);raf.write("周期".getBytes());raf.writeInt(103);raf.close();}public static void writeFile()throws IOException{RandomAccessFile raf = new RandomAccessFile("ran.txt","rw");raf.write("李四".getBytes());raf.writeInt(97);raf.write("王五".getBytes());raf.writeInt(99);raf.close();}
}