java文本输入输出小结

Java 文本输入主要包含两种方法：FileRead -- 按字符读入，InputSreamReader -- 按行输入。

java 文本输出也包含两种方法：FileWriter 和 OuputStreamWriter，这两种都是按字符输出。

应用代码如下：

 package stream.inout;

 import java.io.*;

 public class FileStream {

     public static void main(String a[]){
         String inputfilepath = "E:/in.txt";
         /*
         in.txt data :
             12345
         in2.txt data :
             11
             22
             33
             44
             55
         output1.txt data :
             tttttrrrrreeeeewwwwwqqqqq
         output2.txt data :
             tttrrreeewwwqqq
         */

         //method no.1 =======================================
         try{
             int []input1 = new int[5];
             File inputfile = new File(inputfilepath);
             if(inputfile.isFile() && inputfile.exists()){
                 //这里的读入是按字符读入
                 FileReader fileread = new FileReader(inputfile);
                 int tmp = 0;
                 int i = 0;
                 while((tmp = fileread.read()) != -1){
                     input1[i++] = tmp - '0';
                 }
                 fileread.close();
                 for(i = 0; i < 5; i ++)
                     System.out.println("input1[ " + i +" ]= " + input1[i]);
             }else{
                 System.out.println("file is not exist");
             }
         }catch (Exception e){
             System.err.println("error happened");
             e.printStackTrace();
         }

         //method no.2 =======================================
         try{
             String []input2 = new String[5];
             String input2filepath = "E:/in2.txt";
             File inputfile = new File(input2filepath);
             if(inputfile.isFile() && inputfile.exists()){
                 //这里的读入是按行读入
                 InputStreamReader isr = new InputStreamReader(new FileInputStream(inputfile));
                 BufferedReader br = new BufferedReader(isr);
                 int i = 0;
                 String line = null;
                 //需注意的是每执行一次br.readLine()，就跳入下一行，故引入一个变量来记录
                 while((line = br.readLine()) != null){
                     input2[i++] = line;
                 }
                 br.close();
                 isr.close();
                 for(i = 0; i < 5; i ++)
                     System.out.println("input2[ " + i +" ]= " + input2[i]);

             }else{
                 System.out.println("file is not exist");
             }
         }catch (Exception e){
             System.err.println("error happened");
             e.printStackTrace();
         }

         //output method no.1 ============================
         String outputfile1 = "E:/output1.txt";
         String outputfile2 = "E:/output2.txt";
         try{
             String []output = {"ttttt", "rrrrr", "eeeee", "wwwww", "qqqqq"};
             FileWriter filewriter = new FileWriter(outputfile1, false);
             for(int i = 0; i < 5; i ++){
                 filewriter.write(output[i]);
             }
             filewriter.close();

         }catch (Exception e){
             System.err.println("error happened");
             e.printStackTrace();
         }
         //output method no.2 ============================
         try {
             String []output1 = {"ttt", "rrr", "eee", "www", "qqq"};
             OutputStreamWriter outsw = new OutputStreamWriter(new FileOutputStream(outputfile2));
             BufferedWriter bw = new BufferedWriter(outsw);

             for(int i = 0; i < 5; i ++){
                 bw.write(output1[i]);
             }
             bw.flush();
             bw.close();
             outsw.close();
         } catch (Exception e) {
             // TODO: handle exception
             System.err.println("error happened");
             e.printStackTrace();
         }
     }

 }