Java读写文件方法总结

Java读写文件方法总结

Java的读写文件方法在工作中相信有很多的用处的，本人在之前包括现在都在使用Java的读写文件方法来处理数据方面的输入输出，确实很方便。奈何我的记性实在是叫人着急，很多时候既然都会想不起来怎么写了，不过我的Java代码量也实在是少的可怜，所以应该多多练习。这里做一个总结，集中在一起方面今后查看。

Java读文件

 package 天才白痴梦;

 import java.io.BufferedReader;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileReader;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.io.RandomAccessFile;
 import java.io.Reader;

 public class JavaIO {

     /**
      * 采用的是操作系统底层默认的编码方式，GBK等，非UTF8
      * */

     /**
      * 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
      * */
     public static void readFileByBytes(String filename) {
         File file=new File(filename);
         FileInputStream in=null;
         try {
             System.out.println("以字节为单位读取文件,一次读一个字节: ");
             in=new FileInputStream(file);
             int temp=0;
             while ((temp=in.read()) != -1) {
                 System.out.println(temp);
             }
             in.close();
         } catch (IOException e) {
             e.printStackTrace();
             return ;
         }
         try {
             System.out.println("以字节为单位读取文件，一次读多个字节： ");
             byte[] temp=new byte[100];
             int byteread=0;
             in=new FileInputStream(file);
             JavaIO.showAvailableBytes(in);
             while ((byteread=in.read(temp)) != -1) {
                 System.out.write(temp,0,byteread);
             }
         } catch (Exception e1) {
             e1.printStackTrace();
         } finally {
             if (in != null) {
                 try {
                     in.close();
                 } catch (IOException e1) {

                 }
             }
         }
     }
     /**
      * 以字符为单位读取文件，常用于读文本，数字等类型的文件
      * */
     public static void readFileByChar(String filename) {
         File file=new File(filename);
         Reader reader=null;
         try {
             System.out.println("以字符为单位读取文件内容，一次一个字节：");
             //InputStreamReader类:是字节向字符转换的桥梁
             reader=new InputStreamReader(new FileInputStream(file));
             int temp;
             while ((temp=reader.read()) != -1) {
                 if (((char)temp) != '\r') {
                     System.out.println((char)temp);
                 }
             }
             reader.close();
         } catch (Exception e) {
             e.printStackTrace();
         }
         try {
             System.out.println("以字符为单位读取文件内容，一次读多个字节： ");
             char[] temp=new char[30];
             int charread=0;
             reader=new InputStreamReader(new FileInputStream(filename));
             while ((charread=reader.read(temp)) != -1) {
                 if ((charread == temp.length) && (temp[temp.length-1]!='\r')) {
                     System.out.println(temp);
                 } else {
                     for (int i=0; i<charread; i++) {
                         if (temp[i] == '\r') {
                             break;
                         } else {
                             System.out.println(temp[i]);
                         }
                     }
                 }
             }
         } catch (Exception e) {
             e.printStackTrace();
         } finally {
             if (reader != null) {
                 try {
                     reader.close();
                 } catch (IOException e) {

                 }
             }
         }
     }
     /**
      * 以行为单位读取文件，常用于读面向行的格式化文件
      * */
     public static void readFileByLine(String filename) {
         File file=new File(filename);
         BufferedReader reader=null;
         try {
             System.out.println("以行为单位读取文件内容，一次读一整行： ");
             reader=new BufferedReader(new FileReader(file));
             String temp=null;
             int line=1;
             while ((temp=reader.readLine()) != null) {
                 System.out.println("line " + line + ": " + temp);
                 line++;
             }
             reader.close();
         } catch (IOException e) {
             e.printStackTrace();
         } finally {
             if (reader != null) {
                 try {
                     reader.close();
                 } catch (IOException e) {

                 }
             }
         }
     }
     /**
      * 随机读取文件内容
      * */
     public static void readFileByRandomAccess(String filename) {
         RandomAccessFile randomfile=null;
         try {
             System.out.println("随机读取一段文件内容");
             randomfile=new RandomAccessFile(filename,"r");
             long fileLength=randomfile.length();
             int beginIndex=(fileLength > 4 ? 4 : 0);
             randomfile.seek(beginIndex);
             byte[] bytes=new byte[10];
             int byteread=0;
             while ((byteread=randomfile.read(bytes)) != -1) {
                 System.out.write(bytes,0,byteread);
             }
         } catch (IOException e) {
             e.printStackTrace();
         } finally {
             if (randomfile != null) {
                 try {
                     randomfile.close();
                 } catch (IOException e) {

                 }
             }
         }
     }
     private static void showAvailableBytes(InputStream in) {
         try {
             System.out.println("当前字节输入流中的字节数为：" + in.available());
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
     public static void main(String[] args) {
         String filename="E:\\BaiYiShaoNian.txt";
         JavaIO.readFileByBytes(filename);
         JavaIO.readFileByChar(filename);
         JavaIO.readFileByLine(filename);
         JavaIO.readFileByRandomAccess(filename);
     }
 }

Java写文件

 package 天才白痴梦;

 import java.io.BufferedWriter;
 import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.FileWriter;
 import java.io.IOException;
 import java.io.OutputStreamWriter;

 public class JavaIO2 {

     public static void main(String[] args) throws IOException {
         String Path="E:\\天才白痴梦\\JAVA";
         File file=new File("E:\\天才白痴梦\\JAVA","BaiYiShaoNian.txt");
         if (!file.exists()) {
             try {
                 file.createNewFile();
             } catch (IOException e) {
                 e.printStackTrace();
             }
         }
         /**
          * Java写入文件的三种方法
          * */
         FileOutputStream fos=null;
         BufferedWriter bw=null;
         FileWriter fw=null;
         int value=1000;

         try {
             fos=new FileOutputStream(new File(Path+"fos.txt"));
             long begin=System.currentTimeMillis();
             for (int i=1; i<=value; i++) {
                 fos.write(5);
             }
             long end=System.currentTimeMillis();
             System.out.println("TheCostTime of FileOutputStream is : " + (end-begin));
             fos.close();

             bw=new BufferedWriter(new OutputStreamWriter(new FileOutputStream(new File(Path+"br.txt")),"UTF8"));
             begin=System.currentTimeMillis();
             for (int i=1; i<=value; i++) {
                 bw.write(5);
                 bw.newLine();
             }
             bw.close();
             end=System.currentTimeMillis();
             System.out.println("TheCostTime of BufferedWriter is : " + (end-begin));

             fw=new FileWriter(Path+"fw.txt");
             begin=System.currentTimeMillis();
             for (int i=1; i<=value; i++) {
                 fw.write(5);
             }
             fw.close();
             end=System.currentTimeMillis();
             System.out.println("TheCostTime of FileWriter is : " + (end-begin));

         } catch (Exception e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         } finally {
             try {
                 fos.close(); //FileOutputStream
                 bw.close(); //BufferedWriter
                 fw.close(); //FileWriter
             } catch (Exception e) {
                 e.printStackTrace();
             }
         }

     }
 }