Java读写文件方法总结

  1 package 天才白痴梦;  2   3 import java.io.BufferedReader;  4 import java.io.File;  5 import java.io.FileInputStream;  6 import java.io.FileReader;  7 import java.io.IOException;  8 import java.io.InputStream;  9 import java.io.InputStreamReader; 10 import java.io.RandomaccessFile; 11 import java.io.Reader; 12  13 public class JavaIO { 14      15     /** 16      * 采用的是操作系统底层默认的编码方式，GBK等，非UTF8 17      * */ 18      19     /** 20      * 以字节为单位读取文件内容，常用于读取二进制文件，比如图片、影像、声音等文件 21      * */ 22     public static void readFileByBytes(String filename) { 23         File file=new File(filename); 24         FileInputStream in=null; 25         try { 26             System.out.PRintln("以字节为单位读取文件,一次读一个字节: "); 27             in=new FileInputStream(file); 28             int temp=0; 29             while ((temp=in.read()) != -1) { 30                 System.out.println(temp); 31             } 32             in.close(); 33         } catch (IOException e) { 34             e.printStackTrace(); 35             return ; 36         } 37         try { 38             System.out.println("以字节为单位读取文件，一次读多个字节： "); 39             byte[] temp=new byte[100]; 40             int byteread=0; 41             in=new FileInputStream(file); 42             JavaIO.showAvailableBytes(in); 43             while ((byteread=in.read(temp)) != -1) { 44                 System.out.write(temp,0,byteread); 45             } 46         } catch (Exception e1) { 47             e1.printStackTrace(); 48         } finally { 49             if (in != null) { 50                 try { 51                     in.close(); 52                 } catch (IOException e1) { 53                      54                 } 55             } 56         } 57     } 58     /** 59      * 以字符为单位读取文件，常用于读文本，数字等类型的文件 60      * */ 61     public static void readFileByChar(String filename) { 62         File file=new File(filename); 63         Reader reader=null; 64         try { 65             System.out.println("以字符为单位读取文件内容，一次一个字节："); 66             //InputStreamReader类:是字节向字符转换的桥梁 67             reader=new InputStreamReader(new FileInputStream(file)); 68             int temp; 69             while ((temp=reader.read()) != -1) { 70                 if (((char)temp) != '/r') { 71                     System.out.println((char)temp); 72                 } 73             }  74             reader.close(); 75         } catch (Exception e) { 76             e.printStackTrace(); 77         } 78         try { 79             System.out.println("以字符为单位读取文件内容，一次读多个字节： "); 80             char[] temp=new char[30]; 81             int charread=0; 82             reader=new InputStreamReader(new FileInputStream(filename)); 83             while ((charread=reader.read(temp)) != -1) { 84                 if ((charread == temp.length) && (temp[temp.length-1]!='/r')) { 85                     System.out.println(temp); 86                 } else { 87                     for (int i=0; i<charread; i++) { 88                         if (temp[i] == '/r') { 89                             break; 90                         } else { 91                             System.out.println(temp[i]); 92                         } 93                     } 94                 } 95             } 96         } catch (Exception e) { 97             e.printStackTrace(); 98         } finally { 99             if (reader != null) {100                 try {101                     reader.close();102                 } catch (IOException e) {103                     104                 }105             }106         }107     }108     /**109      * 以行为单位读取文件，常用于读面向行的格式化文件110      * */111     public static void readFileByLine(String filename) {112         File file=new File(filename);113         BufferedReader reader=null;114         try {115             System.out.println("以行为单位读取文件内容，一次读一整行： ");116             reader=new BufferedReader(new FileReader(file));117             String temp=null;118             int line=1;119             while ((temp=reader.readLine()) != null) {120                 System.out.println("line " + line + ": " + temp);121                 line++;122             }123             reader.close();124         } catch (IOException e) {125             e.printStackTrace();126         } finally {127             if (reader != null) {128                 try {129                     reader.close();130                 } catch (IOException e) {131                     132                 }133             }134         }135     }136     /**137      * 随机读取文件内容138      * */139     public static void readFileByRandomAccess(String filename) {140         RandomAccessFile randomfile=null;141         try {142             System.out.println("随机读取一段文件内容");143             randomfile=new RandomAccessFile(filename,"r");144             long fileLength=randomfile.length();145             int beginIndex=(fileLength > 4 ? 4 : 0);146             randomfile.seek(beginIndex);147             byte[] bytes=new byte[10];148             int byteread=0;149             while ((byteread=randomfile.read(bytes)) != -1) {150                 System.out.write(bytes,0,byteread);151             }152         } catch (IOException e) {153             e.printStackTrace();154         } finally {155             if (randomfile != null) {156                 try {157                     randomfile.close();158                 } catch (IOException e) {159                     160                 }161             }162         }163     }164     private static void showAvailableBytes(InputStream in) {165         try {166             System.out.println("当前字节输入流中的字节数为：" + in.available());167         } catch (IOException e) {168             e.printStackTrace();169         }170     }171     public static void main(String[] args) {172         String filename="E://BaiYiShaoNian.txt";173         JavaIO.readFileByBytes(filename);174         JavaIO.readFileByChar(filename);175         JavaIO.readFileByLine(filename);176         JavaIO.readFileByRandomAccess(filename);177     }178 }

 1 package 天才白痴梦; 2  3 import java.io.BufferedWriter; 4 import java.io.File; 5 import java.io.FileNotFoundException; 6 import java.io.FileOutputStream; 7 import java.io.FileWriter; 8 import java.io.IOException; 9 import java.io.OutputStreamWriter;10 11 public class JavaIO2 {12 13     public static void main(String[] args) throws IOException {14         String Path="E://天才白痴梦//JAVA";15         File file=new File("E://天才白痴梦//JAVA","BaiYiShaoNian.txt");16         if (!file.exists()) {17             try {18                 file.createNewFile();19             } catch (IOException e) {20                 e.printStackTrace();21             }22         }23         /**24          * Java写入文件的三种方法25          * */26         FileOutputStream fos=null;27         BufferedWriter bw=null;28         FileWriter fw=null;29         int value=1000;30         31         try {32             fos=new FileOutputStream(new File(Path+"fos.txt"));33             long begin=System.currentTimeMillis();34             for (int i=1; i<=value; i++) {35                 fos.write(5);36             }37             long end=System.currentTimeMillis();38             System.out.println("TheCostTime of FileOutputStream is : " + (end-begin));39             fos.close();40             41             bw=new BufferedWriter(new OutputStreamWriter(new FileOutputStream(new File(Path+"br.txt")),"UTF8"));42             begin=System.currentTimeMillis();43             for (int i=1; i<=value; i++) {44                 bw.write(5);45                 bw.newLine();46             }47             bw.close();48             end=System.currentTimeMillis();49             System.out.println("TheCostTime of BufferedWriter is : " + (end-begin));50             51             fw=new FileWriter(Path+"fw.txt");52             begin=System.currentTimeMillis();53             for (int i=1; i<=value; i++) {54                 fw.write(5);                55             }56             fw.close();57             end=System.currentTimeMillis();58             System.out.println("TheCostTime of FileWriter is : " + (end-begin));59             60             61         } catch (Exception e) {62             // TODO Auto-generated catch block63             e.printStackTrace();64         } finally {65             try {66                 fos.close(); //FileOutputStream67                 bw.close(); //BufferedWriter68                 fw.close(); //FileWriter69             } catch (Exception e) {70                 e.printStackTrace();71             }72         }73         74     }75 }