黑马程序员 Java输入\输出

File类

构造方法摘要：

File(File parent,String child)
File(String pathname)
File(String parent,String child)

 1 import java.io.*;
 2 class FileDemo 
 3 {
 4     public static void main(String[] args) 
 5     {
 6         File f1=new File("a.txt");
 7         File f2=new File("c:"+File.separator+"aa"+File.separator+"dd","b.txt");
 8         File f3=new File("c:"+File.separator+"aa"+File.separator+"dd");
 9         File f4=new File(f3,"b.txt");
10         System.out.println(f1);
11         System.out.println(f2);
12         System.out.println(f4);
13     }
14 }
15 /*
16 a.txt
17 c:\aa\dd\b.txt
18 c:\aa\dd\b.txt
19 */

创建方法摘要：

boolean createNewFile()
boolean mkdir()
boolean mkdirs() 创建多级目录

删除方法

boolean delete()
void deleteOnExit()

判断方法摘要：

boolean equals(Object obj)测试路径是否相等
boolean canExecute() 判断文件是否可执行
boolean canRead()
boolean canWrite()
boolean isHidden
boolean isFile()
boolean isDirectory()
boolean isAbsolute()
int compareTo(File pathname)
boolean exists()

获取方法摘要：

String getName()
String getPath() 获取相对路径
String getAbsoluteFile()获取绝对路径
String getParent() 返回父目录
String[] list()
String[] list(FilenameFilter filter)

 1 import java.io.*;
 2 class FileDemo3 
 3 {
 4     public static void main(String[] args) 
 5     {
 6         File f=new File("F:\\音樂\\华语");
 7         String[]  fileNames=f.list(new FilenameFilter()
 8         {
 9             public boolean accept(File f,String name)
10             {
11                 return name.endsWith(".ape");
12             }
13         });
14         for (String fileName:fileNames)
15         {
16             System.out.println(fileName);
17         }
18         System.out.println(fileNames.length);
19     }
20 }

利用递归获取目录中的所有文件

 1 import java.io.*;
 2 class FileDemo4 
 3 {
 4     public static void main(String[] args) 
 5     {
 6         File dir=new File("G:\\java");
 7         showDir(dir);
 8     }
 9     public static void showDir(File dir)
10     {
11         System.out.println(dir);
12         File[] files =dir.listFiles();
13         for (int x=0;x<files.length ;x++ )
14         {
15             if (files[x].isDirectory())
16                 showDir(files[x]);
17             else
18                 System.out.println(files[x]);
19         }
20     }
21 }

FileWriter

方法摘要

void write(String str,int off,int len)
void write(int c)
void write(char[] cbuf,in off,int len)
void close()
void flush()

 1 import java.io.*;
 2 class FileWriterDemo2 
 3 {
 4     public static void main(String[] args) 
 5     {   
 6         FileWriter fw=null;
 7         try
 8         {
 9             fw=new FileWriter("3.txt");
10             fw.write("adhf");
11         }
12         catch (IOException e)
13         {
14             System.out.println(e.toString());
15         }
16         finally
17         {
18             if(fw!=null)
19             fw.close();
20         }
21     }
22 }

传递一个true参数，代表不覆盖已有文件，并在已有文件末尾进行文件的续写。

1  fw=new FileWriter("2.txt",true);

FileReader

int read() 读取单个字符如果达到流的末尾返回-1

 1 import java.io.*;
 2 class FileReaderDemo3 
 3 {
 4     public static void main(String[] args) 
 5     {
 6         FileReader fr =null;
 7         try
 8         {
 9             fr =new FileReader("ma.txt");
10             int ch = 0;
11             while ((ch=fr.read())!=-1)
12             {
13                 System.out.print((char)ch);
14             }
15         }
16         catch (IOException e)
17         {
18             e.printStackTrace();
19         }
20         finally
21         {
22             try
23             {
24                 if(fr!=null)
25                     fr.close();
26             }
27             catch (IOException e)
28             {
29                 e.printStackTrace();
30             }
31         }
32     }
33 }

int read(char[] cbuf )

 1 import java.io.*;
 2 class  FileReaderDemo5
 3 {
 4     public static void main(String[] args) throws IOException
 5     {
 6         FileReader fr=new FileReader("ma.txt");//ma内容 daskfjklashahd
 7         //定义一个字符数组，用于存储读到字符
 8         char[] buf=new char[3];
 9         //read(char[])返回的是读到字符个数
10         int num=fr.read(buf);
11         System.out.println(num);
12         System.out.println(new String(buf,0,num));
13         num=fr.read(buf);
14         System.out.println(num);
15         System.out.println(new String(buf,0,num));
16         num=fr.read(buf);
17         System.out.println(num);
18         System.out.println(new String(buf,0,num));
19         num=fr.read(buf);
20         System.out.println(num);
21         System.out.println(new String(buf,0,num));
22         num=fr.read(buf);
23         System.out.println(num);
24         System.out.println(new String(buf,0,num));
25         num=fr.read(buf);
26         System.out.println(num);
27         System.out.println(new String(buf,0,num));
28         fr.close();
29     }
30 }
31 /*
32 3
33 das
34 3
35 kfj
36 3
37 kla
38 3
39 sha
40 2
41 hd
42 -1
43 Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String ind
44 ex out of range: -1
45         at java.lang.String.<init>(String.java:226)
46         at FileReaderDemo5.main(FileReaderDemo5.java:27)
47 */

 1 import java.io.*;
 2 class FileReaderDemo6
 3 {
 4     public static void main(String args[])
 5     {
 6         FileReader fr =null;
 7         try
 8         {
 9             fr=new FileReader("ma.txt");
10             char[] cbuf =new char[1024];
11             int num;
12             while ((num=fr.read(cbuf))!=-1)
13             {
14                 System.out.println(new String(cbuf,0,num));
15             }
16         }
17         catch (IOException e)
18         {
19             e.printStackTrace();
20         }
21         finally
22         {
23             try
24             {
25                 if(fr!=null)
26                     fr.close();
27             }
28             catch (IOException e)
29             {
30                 e.printStackTrace();
31             }
32         }
33     }
34 }

复制文件

import java.io.*;
class CopyDemo
{
    public static void main(String[] args) 
    {
        copy();
    }
    public static void copy()
    {
        FileWriter fw=null;
        FileReader fr=null;
        try
        {
            fw =new FileWriter("1_copy.txt");
            fr =new FileReader("1.txt");
            char[] buf=new char[1024];
            int len=0;
            while ((len=fr.read(buf))!=-1)
            {
                fw.write(buf,0,len);
            }
        }
        catch (IOException e)
        {
            throw new RuntimeException("读写失败");
        }
        finally
        {
            
                try
                {
                    if(fr!=null)
                        fr.close();
                }
                catch (IOException e)
                {
                    e.printStackTrace();
                }
            
                try
                {
                    if (fw!=null)
                        fw.close();
                }
                catch (IOException e)
                {
                    e.printStackTrace();
                }
        }
    }
}

BufferedWriter

 1 import java.io.*;
 2 class BufferedWriterDemo2 
 3 {
 4     public static void main(String[] args) 
 5     {
 6         FileWriter fw =null;
 7         BufferedWriter bw=null;
 8         try
 9         {
10             fw =new FileWriter("ma.txt");
11             bw =new BufferedWriter(fw);
12             for (int x=0;x<5 ;x++ )
13             {
14                 bw.write("abc"+x);
15                 bw.newLine();
16                 bw.flush();
17             }
18         }
19         catch (IOException e)
20         {
21             e.printStackTrace();
22         }
23         finally
24         {
25             try
26             {
27                 if (bw!=null)
28                     bw.close();
29                 
30             }
31             catch (IOException e)
32             {
33                 e.printStackTrace();
34             }
35         }
36     }

BufferedReader

import java.io.*;
class BufferedReaderDemo2 
{
    public static void main(String[] args) 
    {
        BufferedReader br=null;
        try
        {
            br =new BufferedReader(new FileReader("ma.txt"));
            String str=null;
            while ((str=br.readLine())!=null)
            {
                System.out.println(str);
            }
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
        finally
        {
            try
            {
                if(br!=null)
                    br.close();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
        }
    }
}

复制文件

 1 /*
 2 readLine方法返回的时候只返回回车符之前的数据内容，并不返回回车符。
 3 */
 4 import java.io.*;
 5 class CopyByBufDemo
 6 {
 7     public static void main(String[] args) 
 8     {
 9         copy();
10     }
11     public static void copy()
12     {
13         BufferedWriter bufw=null;
14         BufferedReader bufr=null;
15         try
16         {
17             bufw =new BufferedWriter(new FileWriter("2_copy.txt"));
18             bufr =new BufferedReader(new FileReader("2.txt"));
19             char[] buf=new char[1024];
20             String str=null;
21             while ((str=bufr.readLine())!=null)
22             {
23                 bufw.write(str);
24                 bufw.newLine();
25                 bufw.flush();
26             }
27         }
28         catch (IOException e)
29         {
30             throw new RuntimeException("读写失败");
31         }
32         finally
33         {
34             
35                 try
36                 {
37                     if(bufr!=null)
38                         bufr.close();
39                 }
40                 catch (IOException e)
41                 {
42                     e.printStackTrace();
43                 }
44             
45                 try
46                 {
47                     if (bufw!=null)
48                         bufw.close();
49                 }
50                 catch (IOException e)
51                 {
52                     e.printStackTrace();
53                 }
54         }
55     }
56 }

/*
字符流
FileReader 
FileWriter
字节流
OutputStream InputStream

*/
import java.io.*;
class  FileStream
{
    public static void main(String[] args) throws IOException
    {
        writeFile();
        readFile_1();
        readFile_2();
    }
    public static void writeFile() throws IOException
    {
        FileOutputStream fos=new FileOutputStream("3.txt");
        fos.write("djfk吗".getBytes());
        fos.close();
    }
    public static void readFile_1() throws IOException
    {
        FileInputStream fis=new FileInputStream("3.txt");
        int ch=0;
        while ((ch=fis.read())!=-1)
        {
            System.out.println((char)ch);
        }
    }
    public static void readFile_2() throws IOException
    {
        FileInputStream fis=new FileInputStream("3.txt");
        byte[] buf=new byte[1024];
        int num=0;
        //read(byte[])返回读到字节的个数
        while ((num=fis.read(buf))!=-1)
        {
            System.out.println(new String(buf,0,num));
        }
    }
}

posted on 2012-06-09 08:25 Lincon Ma 阅读(188) 评论(0) 编辑收藏举报