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 }

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 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 }

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 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 }

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 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 }

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 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 }

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