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();
        }
    }

}