java IO 入门例子

 1 import java.io.File;
 2 
 3 /**
 4  * File类型基本操作
 5  */
 6 
 7 /**
 8  * @author Administrator
 9  * 
10  */
11 public class FileDemo {
12 
13     /**
14      * @param args
15      */
16     public static void main(String[] args) {
17         // TODO Auto-generated method stub
18         final String PATH = "c:\text.txt";
19         File file = new File(PATH);
20         if (file.exists()) {
21             if (file.isFile()) {
22                 System.out.println("名称：" + file.getName());
23                 System.out.println("相对路径：" + file.getPath());
24                 System.out.println("绝对路径：" + file.getAbsolutePath());
25                 System.out.println("文件大小：" + file.length() + "字节");
26             } else if (file.isDirectory()) {
27                 System.out.println("这是一个目录！");
28             }
29         } else {
30             System.out.println("文件不存在！");
31         }
32     }
33 
34 }
View Code
 1 import java.io.FileInputStream;
 2 import java.io.FileOutputStream;
 3 
 4 /**
 5  * 使用字节流写入文件、读取文件。
 6  */
 7 /**
 8  * @author Administrator
 9  * 
10  */
11 public class ByteStreamDemo {
12 
13     /**
14      * @param args
15      * @throws Exception
16      */
17     public static void main(String[] args) throws Exception {
18         // TODO Auto-generated method stub
19         final String PATH = "c:\text.txt";
20         
21         FileOutputStream fos = null;
22         try {
23             String content = "王云鹏是帅哥！";
24             byte[] contents = content.getBytes();
25             fos = new FileOutputStream(PATH);
26             fos.write(contents, 0, contents.length);
27             fos.flush();
28         } catch (Exception e) {
29             // TODO: handle exception
30             throw e;
31         } finally {
32             if (fos != null) {
33                 fos.close();
34             }
35         }
36         
37         FileInputStream fis = null;
38         try {
39             fis = new FileInputStream(PATH);
40             int length = fis.available();
41             byte[] contents = new byte[length];
42             while(fis.read(contents, 0, length)!=-1){
43                 String content = new String(contents);
44                 System.out.println(content);
45             }
46         } catch (Exception e) {
47             // TODO: handle exception
48             throw e;
49         }
50         finally{
51             if(fis!=null){
52                 fis.close();
53             }
54         }
55     }
56 
57 }
View Code
 1 import java.io.DataInputStream;
 2 import java.io.DataOutputStream;
 3 import java.io.FileInputStream;
 4 import java.io.FileOutputStream;
 5 
 6 /**
 7  * 采用二进制流方式写入文件、读取文件。
 8  */
 9 
10 /**
11  * @author Administrator
12  * 
13  */
14 public class BinaryStreamDemo2 {
15 
16     /**
17      * @param args
18      * @throws Exception
19      */
20     public static void main(String[] args) throws Exception {
21         // TODO Auto-generated method stub
22         final String PATH = "c:\text.txt";
23         
24         java.io.FileOutputStream fos = null;
25         java.io.DataOutputStream dos = null;
26         try {
27             fos = new FileOutputStream(PATH);
28             dos = new DataOutputStream(fos);
29 
30             dos.writeInt(1);
31             dos.writeLong(2);
32             dos.writeUTF("王云鹏是帅哥！");
33             dos.flush();
34 
35         } catch (Exception e) {
36             // TODO: handle exception
37             throw e;
38         } finally {
39             if (dos != null) {
40                 dos.close();
41             }
42             if (fos != null) {
43                 fos.close();
44             }
45         }
46 
47         java.io.FileInputStream fis = null;
48         java.io.DataInputStream dis = null;
49         try {
50             fis = new FileInputStream(PATH);
51             dis = new DataInputStream(fis);
52 
53             int i = dis.readInt();
54             long l = dis.readLong();
55             String content = dis.readUTF();
56             System.out.println(i);
57             System.out.println(l);
58             System.out.println(content);
59         } catch (Exception e) {
60             // TODO: handle exception
61             throw e;
62         } finally {
63             if (dis != null) {
64                 dis.close();
65             }
66             if (fis != null) {
67                 fis.close();
68             }
69         }
70     }
71 
72 }
View Code
 1 import java.io.DataInputStream;
 2 import java.io.DataOutputStream;
 3 import java.io.FileInputStream;
 4 import java.io.FileOutputStream;
 5 
 6 /**
 7  * 采用二进制流方式写入文件、读取文件。
 8  */
 9 
10 /**
11  * @author Administrator
12  *
13  */
14 public class BinaryStreamDemo {
15 
16     /**
17      * @param args
18      * @throws Exception 
19      */
20     public static void main(String[] args) throws Exception {
21         // TODO Auto-generated method stub
22         java.io.FileOutputStream fos = null;
23         java.io.DataOutputStream dos = null;
24         java.io.FileInputStream fis = null;
25         java.io.DataInputStream dis = null;
26         try {
27             fis = new FileInputStream("c:\source.jpg");
28             dis = new DataInputStream(fis);
29             
30             fos = new FileOutputStream("c:\desc.jpg");
31             dos = new DataOutputStream(fos);
32             
33             int temp = -1;
34             while((temp=dis.read())!=-1){
35                 dos.write(temp);
36             }
37         } catch (Exception e) {
38             // TODO: handle exception
39             throw e;
40         }
41         finally
42         {
43             if(dos!=null)
44             {
45                 dos.close();
46             }
47             if(fos!=null){
48                 fos.close();
49             }
50             if(dis!=null){
51                 dis.close();
52             }
53             if(fis!=null){
54                 fis.close();
55             }
56         }
57         System.out.println("copy file success!");
58     }
59 
60 }
View Code
 1 import java.io.FileReader;
 2 import java.io.FileWriter;
 3 import java.io.IOException;
 4 import java.util.Arrays;
 5 
 6 /**
 7  * 使用字符流写入文件、读取文件。
 8  */
 9 
10 /**
11  * @author Administrator
12  *
13  */
14 public class CharStreamDemo {
15 
16     /**
17      * @param args
18      * @throws Exception 
19      */
20     public static void main(String[] args) throws Exception {
21         // TODO Auto-generated method stub
22         final String PATH = "c:\text.txt";
23         
24         FileWriter fw = null;
25         try{
26             fw = new FileWriter(PATH);
27             fw.write("王云鹏是帅哥！");
28             fw.flush();
29         }catch(IOException ex){
30             throw ex;
31         }
32         finally{
33             if(fw!=null){
34                 fw.close();
35             }
36         }
37         
38         FileReader fr = null;
39         try {
40             fr = new FileReader(PATH);
41             char[] chars = new char[1024];
42             StringBuilder sb = new StringBuilder();
43             int length = 0;
44             while((length=fr.read(chars))!=-1){
45                 if(length==1024){
46                     sb.append(chars);
47                 }else
48                 {
49                     char[] less = Arrays.copyOf(chars, length);
50                     sb.append(less);
51                 }
52                 Arrays.fill(chars, ' ');//清空数组
53             }
54             System.out.println(sb.toString());
55             
56         } catch (Exception e) {
57             // TODO: handle exception
58             throw e;
59         }
60         finally{
61             if(fr!=null){
62                 fr.close();
63             }
64         }
65     }
66 
67 }
View Code
 1 import java.io.BufferedReader;
 2 import java.io.BufferedWriter;
 3 import java.io.FileReader;
 4 import java.io.FileWriter;
 5 
 6 /**
 7  * 使用字符流+缓冲器写入文件、读取文件。
 8  */
 9 
10 /**
11  * @author Administrator
12  * 
13  */
14 public class CharBufferStreamDemo {
15 
16     /**
17      * @param args
18      * @throws Exception
19      */
20     public static void main(String[] args) throws Exception {
21         // TODO Auto-generated method stub
22         final String PATH = "c:\text.txt";
23 
24         FileWriter fw = null;
25         BufferedWriter bw = null;
26         try {
27             fw = new FileWriter(PATH);
28             bw = new BufferedWriter(fw);
29             bw.write("王云鹏是帅哥！");
30             bw.newLine();
31             bw.write("王云鹏是北大青鸟趟城中心的帅哥！");
32             bw.flush();
33         } catch (Exception e) {
34             // TODO: handle exception
35             throw e;
36         } finally {
37             if (bw != null) {
38                 bw.close();
39             }
40             if (fw != null) {
41                 fw.close();
42             }
43         }
44 
45         FileReader fr = null;
46         BufferedReader br = null;
47         try {
48             fr = new FileReader(PATH);
49             br = new BufferedReader(fr);
50             String line = null;
51             while ((line = br.readLine()) != null) {
52                 System.out.println(line);
53             }
54         } catch (Exception e) {
55             // TODO: handle exception
56             throw e;
57         } finally {
58             if (br != null) {
59                 br.close();
60             }
61             if (fr != null) {
62                 fr.close();
63             }
64         }
65     }
66 
67 }
View Code
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原文地址：https://www.cnblogs.com/qiyebao/p/3642325.html