java 文件操作

一、获取文件列表

　　方法一：DirFilter类实现了FilenameFilter接口，需要重写FilenamFilter中的accept方法。

 1 /**
 2  * java文件操作  获取文件列表
 3  * 2016/6/15
 4  */
 5 package fileStream;
 6 
 7 import java.io.File;
 8 import java.io.FilenameFilter;
 9 import java.util.regex.*;
10 import java.util.*;
11 
12 public class DirList {
13     public static void main(String[] args){
14         File path = new File("G:");
15         String[] list;
16         if(args.length == 0){
17             list = path.list();
18         }else{
19             list = path.list(new DirFilter(args[0]));
20         }
21         Arrays.sort(list, String.CASE_INSENSITIVE_ORDER);
22         for(String dirItem:list){
23             System.out.println(dirItem);
24         }
25     }
26 }
27 
28 class DirFilter implements FilenameFilter {
29     private Pattern pattern;
30     public DirFilter(String regex){
31         pattern = Pattern.compile(regex);
32     }
33     @Override
34     public boolean accept(File dir, String name) {
35         return pattern.matcher(name).matches();
36     }
37 }
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　　方法二：使用匿名内部类

 1 /**
 2  * 获取文件列表方法2  匿名内部类
 3  * 2016/6/15
 4  */
 5 package fileStream;
 6 
 7 import java.io.*;
 8 import java.util.*;
 9 import java.util.regex.*;
10 
11 
12 public class DirList2 {
13     public static FilenameFilter filter(final String regex){
14         return new FilenameFilter(){
15             private Pattern pattern = Pattern.compile(regex);
16             @Override
17             public boolean accept(File dir, String name){
18                 return pattern.matcher(name).matches();
19             }
20         };
21     }
22     public static void main(String[] args){
23         File path = new File("G:");
24         String[] list;
25         if(args.length == 0){
26             list = path.list();
27         }else{
28             list = path.list(new DirFilter(args[0]));
29         }
30         Arrays.sort(list, String.CASE_INSENSITIVE_ORDER);
31         for(String dirItem:list){
32             System.out.println(dirItem);
33         }
34     }
35 
36 }
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　　方法二改进：

 1 /**
 2  * Thinking in Java
 3  * 获取文件列表  方法二改进
 4  * 2016/6/15
 5  */
 6 package fileStream;
 7 
 8 import java.util.*;
 9 import java.util.regex.*;
10 import java.io.*;
11 
12 public class DirList3 {
13     public static void main(final String[] args){
14         File path = new File("G:");
15         String[] list;
16         if(args.length == 0){
17             list = path.list();
18         }else{
19             list = path.list(new FilenameFilter() {
20                 private Pattern pattern = Pattern.compile(args[0]);
21                 public boolean accept(File dir, String name) {
22                     return pattern.matcher(name).matches();
23                 }
24             });
25         }
26             Arrays.sort(list, String.CASE_INSENSITIVE_ORDER);
27             for(String dirItem : list){
28                 System.out.println(dirItem);
29             }
30     }
31 }
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二、文本文件的读写

 1 /**
 2  * 文本文件的读写
 3  * 2016/6/15
 4  */
 5 package fileStream;
 6 
 7 import java.io.BufferedReader;
 8 import java.io.FileOutputStream;
 9 import java.io.FileReader;
10 import java.io.IOException;
11 import java.util.Scanner;
12 
13 
14 public class FileStream {
15     public static void main(String[] args) throws IOException{
16         //写入文件
17         FileOutputStream outFile = new FileOutputStream("E:/1.txt",true);
18         StringBuffer outText = new StringBuffer();
19         String str = null;
20         Scanner input = new Scanner(System.in);
21         byte[] writeByte = null;
22         while(true){
23             str = input.nextLine();
24             outText.append(str);
25             if(str.equals("quit")) break;
26         }
27         
28         writeByte = (outText+"").getBytes();
29         outFile.write(writeByte);
30         outFile.close();
31         
32         //读取文件
33         BufferedReader  reader = new BufferedReader(new FileReader("E:/1.txt"));
34         String text = null;    
35         while((text = reader.readLine()) != null){
36             System.out.println(text);
37         }
38         reader.close();
39     }
40 }
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三、二进制文件的读取 

 1 //此处只提供方法，主函数请自行书写
 2 public static byte[] read(File bfile) throws IOException {
 3         BufferedInputStream bf = new BufferedInputStream(new FileInputStream(bfile));
 4         try {
 5             byte[] data = new byte[bf.available()];
 6             bf.read(data);
 7             return data;
 8         } catch (Exception e) {
 9             // TODO: handle exception
10         }finally{
11             bf.close();
12         }
13         return null;
14     }
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四、进程控制

　　传入操作系统的命令，后台运行后获取输出，并打印出来。

 1 /**
 2  * Thinking in Java
 3  * 进程控制  运行操作系统命令，发送输出到控制台
 4  * 2016/6/16
 5  */
 6 package fileStream;
 7 import java.io.*;
 8 
 9 public class OSExecute {
10     public static void command(String command) {
11         boolean err = false;
12         try {
13             //创建一个新的Process实例
14             Process process = new ProcessBuilder(command.split(" ")).start();
15             BufferedReader results = new BufferedReader(new InputStreamReader(process.getInputStream()));
16             String s;
17             while((s = results.readLine()) != null){
18                 System.out.println(s);
19             }
20             //获取错误信息
21             BufferedReader errors = new BufferedReader(
22                     new InputStreamReader(process.getErrorStream()));
23             while ((s = errors.readLine()) != null) {
24                 System.err.println(s);
25                 err = true;
26             }
27         }catch(Exception e) {
28             if(!command.startsWith("CMD /C")){
29                 command("CMD /C" + command);
30             }else{
31                 throw new RuntimeException(e);
32             }
33             if(err){
34 //                throw new OSExecuteException("Errors executing " + command);
35             }
36         }
37     }
38     public static void main(String[] args){
39         String path="F:\java\work_1\Stream\bin\fileStream/";  
40         String commandw="javap "+path+"OSExecute.class";  
41         OSExecute.command(commandw);    //传入CMD命令
42     }
43 }
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五、新I/O

JDK1.4中的java.nio.*包引入了行动JavaI/O类库，可以提高读取速度。

 1 /**
 2  * Thinking in Java P552
 3  * java 新I/O
 4  * 2016/6/16
 5  */
 6 package fileStream;
 7 
 8 import java.io.FileInputStream;
 9 import java.io.FileNotFoundException;
10 import java.io.FileOutputStream;
11 import java.io.IOException;
12 import java.io.RandomAccessFile;
13 import java.nio.ByteBuffer;
14 import java.nio.channels.FileChannel;
15 
16 public class GetChannel {
17     private static final int BSIZE = 1024;
18     public static void main(String[] args){
19         try {
20             //写入文件
21             FileChannel  fc = new FileOutputStream("1.txt").getChannel();
22             fc.write(ByteBuffer.wrap("hello world".getBytes()));
23             fc.close();
24             //在文件尾添加内容
25             fc = new RandomAccessFile("1.txt", "rw").getChannel();
26             fc.position(fc.size());        //移动到文件末尾
27             fc.write(ByteBuffer.wrap("More Hello World".getBytes()));
28             fc.close();
29             //读取文件
30             fc = new FileInputStream("1.txt").getChannel();
31             ByteBuffer buff = ByteBuffer.allocate(BSIZE);
32             fc.read(buff);
33             buff.flip();
34             while(buff.hasRemaining()){
35                 System.out.print((char)buff.get());
36             }
37         } catch (FileNotFoundException e) {
38             // TODO Auto-generated catch block
39             e.printStackTrace();
40         } catch (IOException e) {
41             // TODO Auto-generated catch block
42             e.printStackTrace();
43         }
44     }
45     
46 
47 }
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 六、文件复制

 1 /**
 2  * Thinking in Java
 3  * 文件复制
 4  * 2016/6/16
 5  */
 6 package fileStream;
 7 
 8 import java.io.File;
 9 import java.io.FileInputStream;
10 import java.io.FileOutputStream;
11 import java.nio.ByteBuffer;
12 import java.nio.channels.FileChannel;
13 
14 public class ChannelCopy {
15     private static final int BSIZE = 1024;
16     public static void main(String[] args) throws Exception {
17         File sourceFile = new File("1.txt");    //源文件
18         File DestFile = new File("1_copy.txt");    //要复制的目标文件
19 
20         FileChannel in = new FileInputStream(sourceFile).getChannel();
21         FileChannel out = new FileOutputStream(DestFile).getChannel();
22         ByteBuffer buffer = ByteBuffer.allocate(BSIZE);
23         while (in.read(buffer) != -1) {
24             buffer.flip();
25             out.write(buffer);
26             buffer.clear();
27         }
28         in.close();
29         out.close();
30     }
31 
32 }
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七、文件内容替换

 1 /**
 2  * 替换某文件夹下所有以.txt 结尾的文件中的"java"字符串，替换为"****"
 3  */
 4 package com;
 5 
 6 import java.io.BufferedReader;
 7 import java.io.File;
 8 import java.io.FileInputStream;
 9 import java.io.FileNotFoundException;
10 import java.io.FileOutputStream;
11 import java.io.IOException;
12 import java.io.InputStreamReader;
13 import java.io.OutputStreamWriter;
14 import java.io.UnsupportedEncodingException;
15 import java.util.ArrayList;
16 import java.util.List;
17 
18 public class ReadAllFile {
19 
20     // 读取一个文件夹下所有文件及子文件夹下的所有文件
21     public static void readAllFile(String filePath) {
22         File f = new File(filePath);
23         File[] files = f.listFiles(); // 得到f文件夹下面的所有文件。
24         List<File> list = new ArrayList<File>();
25         for (File file : files) {
26             if (file.isDirectory()) {
27                 // 如何当前路劲是文件夹，则循环读取这个文件夹下的所有文件
28                 readAllFile(file.getAbsolutePath());
29             } else {
30                 list.add(file);
31             }
32         }
33         for (File file : files) {
34             String fileName = file.getName();
35             if (fileName.endsWith("txt")) {
36                 // 替换所有的java字符串
37                 replace(file);
38             }
39         }
40     }
41 
42     //替换
43     private static void replace(File file) {
44         InputStreamReader isr;
45         OutputStreamWriter osw;
46         try {
47             isr = new InputStreamReader(new FileInputStream(file), "UTF-8");
48             BufferedReader br = new BufferedReader(isr);
49             String str = "";
50             StringBuffer index = new StringBuffer();
51             while ((str = br.readLine()) != null) {
52                 System.out.println(str);
53                 index.append(str.replaceAll("java", "****") + '
');
54             }
55             osw = new OutputStreamWriter(new FileOutputStream(file), "UTF-8");
56             osw.write(index.toString());
57             osw.flush();
58             br.close();
59         } catch (UnsupportedEncodingException e) {
60             e.printStackTrace();
61         } catch (FileNotFoundException e) {
62             e.printStackTrace();
63         } catch (IOException e) {
64             e.printStackTrace();
65         }
66 
67     }
68 
69     public static void main(String[] args) {
70         String filePath = "F:\Test";
71         readAllFile(filePath);
72     }
73 }
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原文地址：https://www.cnblogs.com/snail-lb/p/5588574.html