1）file.listFiles()返回f目录下的文件数组
2）File.listRoots()返回本地磁盘驱动器的数组
TestFile.java
File类
import java.io.File;import java.text.SimpleDateFormat;public class TestFile { public static void main(String[] args) { File f=new File("e:\\1.txt"); System.out.println(f.exists()); System.out.println(f.canExecute()); System.out.println(f.getName()); System.out.println(f.getFreeSpace()/1024.0/1024/1024); System.out.println(f.listFiles());//（1） SimpleDateFormat smp=new SimpleDateFormat("yy-MM-dd"); System.out.println(smp.format(f.lastModified())); System.out.println(File.listRoots()[3]); //（2） }}
输出：
true
true
1.txt
10.352336883544922
null
09-12-06
F:\
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MyDir.java
制作自己的DIR .对file类的属性方法进行练习。
import java.io.File;import java.text.DecimalFormat;import java.text.SimpleDateFormat;public class MyDir { public static void main(String[] args) { File f = new File("e:\\"); File fs[] = f.listFiles(); for (File file : fs) { Show(file); } } static void Show(File f) { SimpleDateFormat smp = new SimpleDateFormat("yy-MM-dd"); DecimalFormat df = new DecimalFormat("#.0000000MB"); String time = smp.format(f.lastModified()); String isdir = f.isDirectory() ? "<DIR>" : ""; String size = df.format(f.length() / 1024.0 / 1024); String name = f.getName(); System.out.println(String.format("%1$-10s%2$-8s%3$-15s%4$-20s", time , isdir, size, name)); }}
输出：
09-12-06 .0001984MB 1.log
09-12-06 .0000095MB 1.txt
09-12-06 .0009766MB 3.txt
09-12-06 .0000000MB 4.txt
09-12-06 .0000267MB 5.txt
09-12-06 .0000725MB data.txt
09-02-17 <DIR> .0000000MB game
08-10-06 <DIR> .0000000MB GHOST
09-12-06 .0000000MB log.txt
09-11-15 <DIR> .0000000MB movie
09-02-25 <DIR> .0000000MB music
09-12-06 <DIR> .0000000MB myjava
09-12-06 .0000343MB MyLog4j.properties
09-12-06 .0000715MB p.txt
09-12-06 .0000124MB pro.txt
09-04-22 .0004606MB pwk.rar
08-10-06 <DIR> .0000000MB RECYCLER
09-11-29 <DIR> .0000000MB soft_JAVA
70-01-01 <DIR> .0000000MB System Volume Information
09-02-24 .0131836MB Thumbs.db
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IOStreamTest.JAVA
对“E:\\1.TXT”的文件进行读写操作。fileinputstream.read();fileoutputstream.write()
import java.io.*;public class IOStreamTest { public static void main(String[] args) { //输出流 try { OutputStream ops = new FileOutputStream("e:\\1.txt"); ops.write('B'); ops.write('M'); ops.write('W'); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } //输入流 try { InputStream ipts = new FileInputStream("e:\\1.txt"); int i = 0; while (true) { i = ipts.read(); if (i == -1) break; System.out.print((char) i); } } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } }}
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1) 把bis读入的信息写入数组b[]
2) 把b[]数组里面的信息写入bos
3）BufferedInput（Output）Stream为处理流，在节点流外头套了一个套子。 StreamCopy.java
文件按位拷贝
import java.io.*;public class StreamCopy { public static void main(String[] args) { try { InputStream is = new FileInputStream("e:\\1.txt"); InputStream bis = new BufferedInputStream(is); //（3） OutputStream os = new FileOutputStream("e:\\3.txt"); OutputStream bos = new BufferedOutputStream(os); byte b[] = new byte[1024]; while ((bis.read(b)) != -1) {//（1） bos.write(b);//（2） } bos.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } }}
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TestFileReader.java。。。。。。。。。。。。。。。。。。。
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1)类要被读取写入，该类需要实现序列接口
2）PersonOut.java将定义的人物“new Person(9527, "唐伯虎")”，记录到“e:\\data.txt”文件中。PersonIn.java从文件中读出object类。
（transient使用此关键字标记属性，使该属性不被记录。Person 若实现Externalizable接口可以定义读取写入规则。）
Object流
Person.java
import java.io.Serializable;public class Person implements Serializable {//（1） private static final long serialVersionUID = 2894597671409392626L; int id; String name; @Override public String toString() { return this.id+"|"+this.name; } 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 Person(int id, String name) { super(); this.id = id; this.name = name; }}
PersonOut.java
import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.ObjectOutputStream;import java.io.OutputStream;public class PersonOut { public static void main(String[] args) { Person p = new Person(9527, "唐伯虎"); try { OutputStream os = new FileOutputStream("e:\\data.txt"); ObjectOutputStream oos = new ObjectOutputStream(os); oos.writeObject(p); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } }}
PersonIn.java
import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.IOException;import java.io.InputStream;import java.io.ObjectInputStream;public class PersonIn { public static void main(String[] args) { try { InputStream is=new FileInputStream("e:\\data.txt"); ObjectInputStream ois= new ObjectInputStream(is); System.out.println(ois.readObject()); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } }}
输出：
9527|唐伯虎
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Properties类是一类特殊的map集合框架
1）加载读取文件内的属性的方法。Properties.load(),properties.store()
PropertiesLoadTest.java
import java.util.*;import java.io.*;public class PropertiesLoadTest { public static void main(String[] args) { Properties pr = new Properties(); try { pr.load(new FileInputStream("e:\\pro.txt"));//（1） /*pro.txt * b=2（换行）a=1（换行） c=3 */ Set<?> s = pr.keySet(); for (Object object : s) { System.out.println(object + "=" + pr.get(object)); } } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } }}
输出：
b=2
a=1
c=33
PropertiesSendTest.java
import java.util.*;import java.io.*;public class PropertiesSendTest { public static void main(String[] args) { Properties pro= new Properties(); pro.put("122", "alue"); pro.put("120", "aluew"); pro.put("432", "aluewe"); try { pro.store(new FileOutputStream("e:\\p.txt"), "MyComments");//（1） } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } }}
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Log4jDemo.java。。。。。。。。。。。。。。。。。。。
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