java io 操作

IO是JAVASE中非常重要的一块，是面向对象的完美体现，深入学习IO，你将可以领略到很多面向对象的思想。
在公司没活干，复习了一下IO，发现很多都忘记了，所以写的不好，只够初学用。我把我复习过程中写的代码贴出来，大家共同学习，并请多指教指教哈。顺便一起讨论IO
1、文件拷贝

Java code

    
    
    
    

     
     
     
      
     
     
     
     try
     
     
     
      { File inputFile 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      File(args[
     
     
     
     0
     
     
     
     ]); 
     
     
     
     if
     
     
     
      (
     
     
     
     !
     
     
     
     inputFile.exists()) { System.out.println(
     
     
     
     "
     
     
     
     源文件不存在，程序终止
     
     
     
     "
     
     
     
     ); System.exit(
     
     
     
     1
     
     
     
     ); } File outputFile 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      File(args[
     
     
     
     1
     
     
     
     ]); InputStream in 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      FileInputStream(inputFile); OutputStream out 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      FileOutputStream(outputFile); 
     
     
     
     byte
     
     
     
      date[] 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      
     
     
     
     byte
     
     
     
     [
     
     
     
     1024
     
     
     
     ]; 
     
     
     
     int
     
     
     
      temp 
     
     
     
     =
     
     
     
      
     
     
     
     0
     
     
     
     ; 
     
     
     
     while
     
     
     
      ((temp 
     
     
     
     =
     
     
     
      in.read(date)) 
     
     
     
     !=
     
     
     
      
     
     
     
     -
     
     
     
     1
     
     
     
     ) { out.write(date); } in.close(); out.close(); } 
     
     
     
     catch
     
     
     
      (FileNotFoundException e) { 
     
     
     
     //
     
     
     
      TODO Auto-generated catch block
     
     
     
      
     
     
     
      e.printStackTrace(); } 
     
     
     
     catch
     
     
     
      (IOException e) { 
     
     
     
     //
     
     
     
      TODO Auto-generated catch block
     
     
     
      
     
     
     
      e.printStackTrace(); } 
    
    
    
    

2、java读文件:实现统计某一目录下每个文件中出现的字母个数、数字个数、空格个数及行数，除此之外没有其他字符

Java code

    
    
    
    

     
     
     
      String fileName 
     
     
     
     =
     
     
     
      
     
     
     
     "
     
     
     
     D:/date.java.bak
     
     
     
     "
     
     
     
     ; 
     
     
     
     //
     
     
     
      String fileName = "D:/test.qqq";
     
     
     
      
     
     
     
      String line; 
     
     
     
     int
     
     
     
      i 
     
     
     
     =
     
     
     
      
     
     
     
     0
     
     
     
     , j 
     
     
     
     =
     
     
     
      
     
     
     
     0
     
     
     
     , f 
     
     
     
     =
     
     
     
      
     
     
     
     0
     
     
     
     , k 
     
     
     
     =
     
     
     
      
     
     
     
     0
     
     
     
     ; 
     
     
     
     try
     
     
     
      { BufferedReader in 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      BufferedReader(
     
     
     
     new
     
     
     
      FileReader(fileName)); line 
     
     
     
     =
     
     
     
      in.readLine(); 
     
     
     
     while
     
     
     
      (line 
     
     
     
     !=
     
     
     
      
     
     
     
     null
     
     
     
     ) { 
     
     
     
     //
     
     
     
      System.out.println(line);
     
     
     
      
     
     
     
      
     
     
     
     char
     
     
     
      c[] 
     
     
     
     =
     
     
     
      line.toCharArray(); 
     
     
     
     for
     
     
     
      (
     
     
     
     int
     
     
     
      i1 
     
     
     
     =
     
     
     
      
     
     
     
     0
     
     
     
     ; i1 
     
     
     
     <
     
     
     
      c.length; i1
     
     
     
     ++
     
     
     
     ) { 
     
     
     
     //
     
     
     
      如果是字母
     
     
     
      
     
     
     
      
     
     
     
     if
     
     
     
      (Character.isLetter(c[i1])) i
     
     
     
     ++
     
     
     
     ; 
     
     
     
     //
     
     
     
      如果是数字
     
     
     
      
     
     
     
      
     
     
     
     else
     
     
     
      
     
     
     
     if
     
     
     
      (Character.isDigit(c[i1])) j
     
     
     
     ++
     
     
     
     ; 
     
     
     
     //
     
     
     
      是空格
     
     
     
      
     
     
     
      
     
     
     
     else
     
     
     
      
     
     
     
     if
     
     
     
      (Character.isWhitespace(c[i1])) f
     
     
     
     ++
     
     
     
     ; } line 
     
     
     
     =
     
     
     
      in.readLine(); k
     
     
     
     ++
     
     
     
     ; } in.close(); System.out .println(
     
     
     
     "
     
     
     
     字母:
     
     
     
     "
     
     
     
      
     
     
     
     +
     
     
     
      i 
     
     
     
     +
     
     
     
      
     
     
     
     "
     
     
     
     ,数字:
     
     
     
     "
     
     
     
      
     
     
     
     +
     
     
     
      j 
     
     
     
     +
     
     
     
      
     
     
     
     "
     
     
     
     ,空格:
     
     
     
     "
     
     
     
      
     
     
     
     +
     
     
     
      f 
     
     
     
     +
     
     
     
      
     
     
     
     "
     
     
     
     ,行数:
     
     
     
     "
     
     
     
      
     
     
     
     +
     
     
     
      k); } 
     
     
     
     catch
     
     
     
      (IOException e) { e.printStackTrace(); } 
    
    
    
    

3、 从文件（d:\test.txt）中查出字符串”aa”出现的次数

Java code

    
    
    
    

     
     
     
      
     
     
     
     try
     
     
     
      { BufferedReader br 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      BufferedReader(
     
     
     
     new
     
     
     
      FileReader( 
     
     
     
     "
     
     
     
     D:\\test.txt
     
     
     
     "
     
     
     
     )); StringBuilder sb 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      StringBuilder(); 
     
     
     
     while
     
     
     
      (
     
     
     
     true
     
     
     
     ) { String str 
     
     
     
     =
     
     
     
      br.readLine(); 
     
     
     
     if
     
     
     
      (str 
     
     
     
     ==
     
     
     
      
     
     
     
     null
     
     
     
     ) 
     
     
     
     break
     
     
     
     ; sb.append(str); } Pattern p 
     
     
     
     =
     
     
     
      Pattern.compile(
     
     
     
     "
     
     
     
     aa
     
     
     
     "
     
     
     
     ); Matcher m 
     
     
     
     =
     
     
     
      p.matcher(sb); 
     
     
     
     int
     
     
     
      count 
     
     
     
     =
     
     
     
      
     
     
     
     0
     
     
     
     ; 
     
     
     
     while
     
     
     
      (m.find()) { count
     
     
     
     ++
     
     
     
     ; } System.out.println(
     
     
     
     "
     
     
     
     \"aa\"一共出现了
     
     
     
     "
     
     
     
      
     
     
     
     +
     
     
     
      count 
     
     
     
     +
     
     
     
      
     
     
     
     "
     
     
     
     次
     
     
     
     "
     
     
     
     ); } 
     
     
     
     catch
     
     
     
      (FileNotFoundException e) { e.printStackTrace(); } 
     
     
     
     catch
     
     
     
      (IOException e) { e.printStackTrace(); } 
    
    
    
    

4、 三种方法读取文件

Java code

    
    
    
    

     
     
     
      
     
     
     
     try
     
     
     
      { 
     
     
     
     //
     
     
     
      方法一
     
     
     
      
     
     
     
      BufferedReader br 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      BufferedReader(
     
     
     
     new
     
     
     
      FileReader(
     
     
     
     new
     
     
     
      File( 
     
     
     
     "
     
     
     
     D:\\1.xls
     
     
     
     "
     
     
     
     ))); 
     
     
     
     //
     
     
     
      StringBuilder bd = new StringBuilder();
     
     
     
      
     
     
     
      StringBuffer bd 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      StringBuffer(); 
     
     
     
     while
     
     
     
      (
     
     
     
     true
     
     
     
     ) { String str 
     
     
     
     =
     
     
     
      br.readLine(); 
     
     
     
     if
     
     
     
      (str 
     
     
     
     ==
     
     
     
      
     
     
     
     null
     
     
     
     ) { 
     
     
     
     break
     
     
     
     ; } System.out.println(str); bd.append(str); } br.close(); 
     
     
     
     //
     
     
     
      System.out.println(bd.toString()); 
     
     
     
     //
     
     
     
      方法二
     
     
     
      
     
     
     
      InputStream is 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      FileInputStream(
     
     
     
     new
     
     
     
      File(
     
     
     
     "
     
     
     
     d:\\1.xls
     
     
     
     "
     
     
     
     )); 
     
     
     
     byte
     
     
     
      b[] 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      
     
     
     
     byte
     
     
     
     [Integer.parseInt(
     
     
     
     new
     
     
     
      File(
     
     
     
     "
     
     
     
     d:\\1.xls
     
     
     
     "
     
     
     
     ).length() 
     
     
     
     +
     
     
     
      
     
     
     
     ""
     
     
     
     )]; is.read(b); System.out.write(b); System.out.println(); is.close(); 
     
     
     
     //
     
     
     
      方法三
     
     
     
      
     
     
     
      Reader r 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      FileReader(
     
     
     
     new
     
     
     
      File(
     
     
     
     "
     
     
     
     d:\\1.xls
     
     
     
     "
     
     
     
     )); 
     
     
     
     char
     
     
     
      c[] 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      
     
     
     
     char
     
     
     
     [(
     
     
     
     int
     
     
     
     ) 
     
     
     
     new
     
     
     
      File(
     
     
     
     "
     
     
     
     d:\\1.xls
     
     
     
     "
     
     
     
     ).length()]; r.read(c); String str 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      String(c); System.out.print(str); r.close(); } 
     
     
     
     catch
     
     
     
      (RuntimeException e) { 
     
     
     
     //
     
     
     
      TODO Auto-generated catch block
     
     
     
      
     
     
     
      e.printStackTrace(); } 
     
     
     
     catch
     
     
     
      (FileNotFoundException e) { 
     
     
     
     //
     
     
     
      TODO Auto-generated catch block
     
     
     
      
     
     
     
      e.printStackTrace(); } 
     
     
     
     catch
     
     
     
      (IOException e) { 
     
     
     
     //
     
     
     
      TODO Auto-generated catch block
     
     
     
      
     
     
     
      e.printStackTrace(); } 
    
    
    
    

5、三种方法写文件

Java code

    
    
    
    

     
     
     
      
     
     
     
     try
     
     
     
      { PrintWriter pw 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      PrintWriter(
     
     
     
     new
     
     
     
      FileWriter(
     
     
     
     "
     
     
     
     d:\\1.txt
     
     
     
     "
     
     
     
     )); BufferedWriter bw 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      BufferedWriter(
     
     
     
     new
     
     
     
      FileWriter(
     
     
     
     new
     
     
     
      File( 
     
     
     
     "
     
     
     
     d:\\1.txt
     
     
     
     "
     
     
     
     ))); OutputStream os 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      FileOutputStream(
     
     
     
     new
     
     
     
      File(
     
     
     
     "
     
     
     
     d:\\1.txt
     
     
     
     "
     
     
     
     )); 
     
     
     
     //
     
     
     
      1
     
     
     
      
     
     
     
      os.write(
     
     
     
     "
     
     
     
     ffff
     
     
     
     "
     
     
     
     .getBytes()); 
     
     
     
     //
     
     
     
      2 
     
     
     
     //
     
     
     
      bw.write("ddddddddddddddddddddddddd"); 
     
     
     
     //
     
     
     
      3 
     
     
     
     //
     
     
     
      pw.print("你好sssssssssssss");
     
     
     
      
     
     
     
      bw.close(); pw.close(); os.close(); } 
     
     
     
     catch
     
     
     
      (IOException e) { 
     
     
     
     //
     
     
     
      TODO Auto-generated catch block
     
     
     
      
     
     
     
      e.printStackTrace(); } 
    
    
    
    

6、读取文件，并把读取的每一行存入double型数组中

Java code

    
    
    
    

     
     
     
      
     
     
     
     try
     
     
     
      { BufferedReader br 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      BufferedReader(
     
     
     
     new
     
     
     
      FileReader(
     
     
     
     new
     
     
     
      File( 
     
     
     
     "
     
     
     
     d:\\2.txt
     
     
     
     "
     
     
     
     ))); StringBuffer sb 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      StringBuffer(); 
     
     
     
     while
     
     
     
      (
     
     
     
     true
     
     
     
     ) { String str 
     
     
     
     =
     
     
     
      br.readLine(); 
     
     
     
     if
     
     
     
      (str 
     
     
     
     ==
     
     
     
      
     
     
     
     null
     
     
     
     ) { 
     
     
     
     break
     
     
     
     ; } sb.append(str 
     
     
     
     +
     
     
     
      
     
     
     
     "
     
     
     
     、
     
     
     
     "
     
     
     
     ); } String str 
     
     
     
     =
     
     
     
      sb.toString(); String s[] 
     
     
     
     =
     
     
     
      str.split(
     
     
     
     "
     
     
     
     、
     
     
     
     "
     
     
     
     ); 
     
     
     
     double
     
     
     
      d[] 
     
     
     
     =
     
     
     
      
     
     
     
     new
     
     
     
      
     
     
     
     double
     
     
     
     [s.length]; 
     
     
     
     for
     
     
     
      (
     
     
     
     int
     
     
     
      i 
     
     
     
     =
     
     
     
      
     
     
     
     0
     
     
     
     ; i 
     
     
     
     <
     
     
     
      s.length; i
     
     
     
     ++
     
     
     
     ) { d[i] 
     
     
     
     =
     
     
     
      Double.parseDouble(s[i]); } 
     
     
     
     for
     
     
     
      (
     
     
     
     int
     
     
     
      i 
     
     
     
     =
     
     
     
      
     
     
     
     0
     
     
     
     ; i 
     
     
     
     <
     
     
     
      d.length; i
     
     
     
     ++
     
     
     
     ) { System.out.println(d[i]); } br.close(); } 
     
     
     
     catch
     
     
     
      (FileNotFoundException e) { 
     
     
     
     //
     
     
     
      TODO Auto-generated catch block
     
     
     
      
     
     
     
      e.printStackTrace(); } 
     
     
     
     catch
     
     
     
      (IOException e) { 
     
     
     
     //
     
     
     
      TODO Auto-generated catch block
     
     
     
      
     
     
     
      e.printStackTrace(); }