java_IO

java_IO_2

1.字节流 InputStream（抽象类）

 1 package ioStudy;
 2 
 3 import java.io.File;
 4 import java.io.FileInputStream;
 5 import java.io.FileNotFoundException;
 6 import java.io.IOException;
 7 import java.io.InputStream;
 8 
 9 /*
10 1.创建源
11 2.选择流
12 3.操作
13 4.释放资源
14 */
15 public class IOstudy2 {
16     public static void main(String[] args) {
17         File file = new File("test.txt");    //创建源
18 
19         InputStream is = null;
20 
21         try {
22             is = new FileInputStream(file);     //  选择流
23             int temp;
24             while ((temp = is.read()) != -1) {      //一次读一个字节  如果包含中文可能会出现乱码  考虑使用字符流
25                 System.out.print((char) temp);    //操作
26             }
27         } catch (FileNotFoundException e) {
28             // TODO Auto-generated catch block
29             e.printStackTrace();
30         } catch (IOException e) {
31             // TODO Auto-generated catch block
32             e.printStackTrace();
33         }finally {
34             if(is!=null) {
35                 try {
36                     is.close();        //释放资源
37                 } catch (IOException e) {
38                     // TODO Auto-generated catch block
39                     e.printStackTrace();
40                 }
41             }
42         }
43     }
44 }

 1 package ioStudy;
 2 
 3 import java.io.File;
 4 import java.io.FileInputStream;
 5 import java.io.FileNotFoundException;
 6 import java.io.IOException;
 7 import java.io.InputStream;
 8 
 9 /*
10 1.创建源
11 2.选择流
12 3.操作
13 4.释放资源
14 */
15 public class IOstudy3 {
16     public static void main(String[] args) {
17         File file = new File("test.txt");
18         InputStream is = null;
19         try {
20             is = new FileInputStream(file);
21             byte[] buffer = new byte[5];
22             int len;
23             while ((len = is.read(buffer)) != -1) {    //一次读取多个
24                 String s = new String(buffer,0,len);
25                 System.out.print(s);
26             }
27         } catch (FileNotFoundException e) {
28             // TODO Auto-generated catch block
29             e.printStackTrace();
30         } catch (IOException e) {
31             // TODO Auto-generated catch block
32             e.printStackTrace();
33         }finally {
34             if(is!=null) {
35                 try {
36                     is.close();
37                 } catch (IOException e) {
38                     // TODO Auto-generated catch block
39                     e.printStackTrace();
40                 }
41             }
42         }
43     }
44 }

View Code

2.OutputStream

 1 package ioStudy;
 2 
 3 import java.io.File;
 4 import java.io.FileNotFoundException;
 5 import java.io.FileOutputStream;
 6 import java.io.IOException;
 7 import java.io.OutputStream;
 8 
 9 /*
10 1.创建源
11 2.选择流
12 3.操作
13 4.释放资源
14 */
15 public class IOstudy4 {
16     public static void main(String[] args) {
17         File file = new File("output.txt"); // 不存在会自动创建
18         OutputStream os = null;
19 
20         try {
21             os = new FileOutputStream(file,true);  //开启向后追加  不然每次都删掉原来的 再写  默认的是false
22             String temp = "hello world!
";
23             byte[] b = temp.getBytes();
24             os.write(b, 0, b.length);
25             os.flush();   //刷新内存
26         } catch (FileNotFoundException e) {
27             // TODO Auto-generated catch block
28             e.printStackTrace();
29         } catch (IOException e) {
30             // TODO Auto-generated catch block
31             e.printStackTrace();
32         } finally {
33             if (os != null) {
34                 try {
35                     os.close();
36                 } catch (IOException e) {
37                     // TODO Auto-generated catch block
38                     e.printStackTrace();
39                 }
40             }
41         }
42     }
43 }

3.实现文件的copy

 1 package ioStudy;
 2 
 3 import java.io.File;
 4 import java.io.FileInputStream;
 5 import java.io.FileNotFoundException;
 6 import java.io.FileOutputStream;
 7 import java.io.IOException;
 8 import java.io.InputStream;
 9 import java.io.OutputStream;
10 
11 /*
12 1.创建源
13 2.选择流
14 3.操作
15 4.释放资源
16 */
17 public class Copy {
18     public static void main(String[] args) {
19         copy("test.txt","testcopy.txt");
20     }
21 
22     public static void copy(String source, String destination) {
23         File src = new File(source);
24         File dest = new File(destination);
25         InputStream is = null;
26         OutputStream os = null;
27         try {
28             is = new FileInputStream(src);
29             os = new FileOutputStream(dest);
30 
31             byte[] buffer = new byte[1034];
32             int len;
33             while ((len = is.read(buffer)) != -1) {
34                 os.write(buffer, 0, len);
35                 os.flush();
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         } finally {
44             // 流关闭的原则 先打开的后关闭
45             if (os != null) {
46                 try {
47                     os.close();
48                 } catch (IOException e) {
49                     // TODO Auto-generated catch block
50                     e.printStackTrace();
51                 }
52             }
53 
54             if (is != null) {
55                 try {
56                     is.close();
57                 } catch (IOException e) {
58                     // TODO Auto-generated catch block
59                     e.printStackTrace();
60                 }
61             }
62         }
63     }
64 }