对java IO,NIO简单操作

Posted 2020-10-30 hello策

 

　对 IO，NIO的简单操作，详细看如下代码

　1、InputStream,OutputStream是对字节流的操作，Reader,Writer是对字符的操作

    2、对大文件的拷贝使用RandomAccessFile类和NIO

  1 import java.io.*;
  2 import java.nio.ByteBuffer;
  3 import java.nio.channels.FileChannel;
  4 
  5 public class IOWriteRead {
  6 
  7     public static void main(String[] args) {
  8         // 一行一行读取文件内容
  9         //readFile("d:\\a.txt");
 10         // 以字符的方式读取a文件写入到b文件
 11         readFileByReader("d:\\a.txt","d:\\c.txt");
 12         // 以字节的方式读取a文件写入到b文件
 13         //readFileByStream("d:\\a.txt","d:\\c.txt");
 14         //拷贝a文件到b文件
 15         //copyFile("d:\\a.txt","d:\\c.txt");
 16         // 拷贝大文本，使用NIO，RandomAccessFile
 17         //copyBigFile("d:\\a.txt","d:\\c.txt");
 18 
 19     }
 20 
 21 
 22     // 一行一行读取文件内容
 23     public static void readFile(String sourceFile){
 24         BufferedReader br = null;
 25         try {
 26             br = new BufferedReader(new FileReader(sourceFile));
 27             String s;
 28             while (( s = br.readLine()) != null){
 29                 System.out.println(s);
 30             }
 31         } catch (FileNotFoundException e) {
 32             e.printStackTrace();
 33         } catch (IOException e) {
 34             e.printStackTrace();
 35         }finally {
 36             try {
 37                 br.close();
 38             } catch (IOException e) {
 39                 e.printStackTrace();
 40             }
 41         }
 42     }
 43 
 44     // 以字符的方式读取a文件写入到b文件
 45     public static void readFileByReader(String sourceFile,String targetFile){
 46         BufferedReader br =null;
 47         //FileWriter fw = null;
 48         PrintWriter pw = null;
 49         try {
 50             br = new BufferedReader(new FileReader(sourceFile));
 51             //fw = new FileWriter(targetFile);
 52             //pw = new PrintWriter(new FileWriter(targetFile));
 53             pw = new PrintWriter(targetFile);
 54             String s ;
 55             while ((s = br.readLine()) != null){
 56                 //fw.write(s+"\r\n");
 57                 pw.write(s);
 58             }
 59 
 60         } catch (FileNotFoundException e) {
 61             e.printStackTrace();
 62         } catch (IOException e) {
 63             e.printStackTrace();
 64         }finally {
 65             try {
 66                 //fw.close();
 67                 pw.close();
 68                 br.close();
 69             } catch (IOException e) {
 70                 e.printStackTrace();
 71             }
 72         }
 73     }
 74 
 75     // 以字节的方式读取a文件写入到b文件
 76     public static void readFileByStream(String sourceFile,String targetFile){
 77         BufferedInputStream in = null;
 78         BufferedOutputStream out = null;
 79         try {
 80             in = new BufferedInputStream(new FileInputStream(sourceFile));
 81             out = new BufferedOutputStream(new FileOutputStream(targetFile));
 82             int len = in.available();
 83             if(len > 0){
 84                 byte[] bytes = new byte[len];
 85                 in.read(bytes, 0 ,len);
 86                 out.write(bytes);
 87             }
 88         } catch (FileNotFoundException e) {
 89             e.printStackTrace();
 90         } catch (IOException e) {
 91             e.printStackTrace();
 92         }finally {
 93             try {
 94                 out.close();
 95                 in.close();
 96             } catch (IOException e) {
 97                 e.printStackTrace();
 98             }
 99         }
100     }
101 
102     //拷贝a文件到b文件
103     public static void copyFile(String sourceFile,String targetFile){
104         File file = new File(sourceFile);
105         if(!file.exists()){
106             System.out.println(sourceFile+"不存在");
107         }
108             FileInputStream in = null;
109             FileOutputStream out = null;
110             try {
111                 in = new FileInputStream(sourceFile);
112                 out = new FileOutputStream(targetFile);
113                 int len = in.available();
114                 if(len > 0){
115                     byte[] bytes = new byte[len];
116                     in.read(bytes,0 , len);
117                     out.write(bytes);
118                 }
119             } catch (FileNotFoundException e) {
120                 e.printStackTrace();
121             } catch (IOException e) {
122                 e.printStackTrace();
123             }finally {
124                 try {
125                     out.close();
126                     in.close();
127                 } catch (IOException e) {
128                     e.printStackTrace();
129                 }
130             }
131     }
132 
133 
134     // 拷贝大文本，使用NIO，RandomAccessFile
135     public static void copyBigFile(String sourceFile,String targetFile){
136         File file = new File(sourceFile);
137         if(!file.exists()){
138             System.out.println("文件不存在");
139         }
140         FileChannel in =null;
141         FileChannel out =null;
142         try {
143             in = new RandomAccessFile(sourceFile,"r").getChannel();
144             out = new FileOutputStream(targetFile).getChannel();
145             ByteBuffer buffer = ByteBuffer.allocate(20*1024*1024);
146             while (in.read(buffer) != -1){
147                 buffer.flip();
148                 out.write(buffer);
149                 buffer.clear();
150             }
151         } catch (FileNotFoundException e) {
152             e.printStackTrace();
153         } catch (IOException e) {
154             e.printStackTrace();
155         }finally {
156             try {
157                 out.close();
158                 in.close();
159             } catch (IOException e) {
160                 e.printStackTrace();
161             }
162         }
163 
164     }
165 }