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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.txt17 c:\aa\dd\b.txt18 c:\aa\dd\b.txt19 */ 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
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 finally17 {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 finally21 {22 try23 {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 /*32 333 das34 335 kfj36 337 kla38 339 sha40 241 hd42 -143 Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String ind44 ex out of range: -145 at java.lang.String. (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 finally22 {23 try24 {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 finally24 {25 try26 {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 try16 {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 finally33 {34 35 try36 {37 if(bufr!=null)38 bufr.close();39 }40 catch (IOException e)41 {42 e.printStackTrace();43 }44 45 try46 {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)); } }}
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