使用BufferedReader读取本地文件的操作

BufferedReader读取本地文件

在使用BufferedWriter写入文件时，如果忘记关闭文件（close）同时也没有调用flush(),则被写入的文件中是没有内容的。

在关闭文件的同时系统会自动调用flush()

 try {
   File file=new File("c://aa.txt");
   FileInputStream is=new FileInputStream(file);
   
   InputStreamReader reader=new InputStreamReader(is,"GBK");
   BufferedReader br=new BufferedReader(reader);
    String line=null;
   while ((line=br.readLine())!=null) {
    System.out.println(line);
   }
   reader.close();
   br.close();
   is.close();
   
  } catch (Exception e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 }

BufferedReader 读取文件内容，原样输出

1.新建目标类：

package com.xuzhiwen.io;
public class TargetFile {
    public static void main(String[] args) {
        System.out.println("TargetFile.java");
    }
}

2.测试类：

package com.xuzhiwen.io;
import java.io.BufferedReader;
import java.io.FileReader;
public class TestBufferedReader {
    public static void main(String[] args) throws Exception {
        String filepath = "src/com/xuzhiwen/io/TargetFile.java";
        BufferedReader read = new BufferedReader(new FileReader(filepath));
        String s;
        StringBuffer sb = new StringBuffer();
        while((s=read.readLine()) != null){
            sb.append(s+"
");
        }
        read.close();
        System.out.println(sb);
    }
}

3.输出结果为：

使用BufferedReader读取本地文件的操作

4.文件结构树：

使用BufferedReader读取本地文件的操作

5. 将结果用StringReader再读一次：

package com.xuzhiwen.io;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.StringReader;
public class TestBufferedReader {
    public static void main(String[] args) throws Exception {
        String filepath = "src/com/xuzhiwen/io/TargetFile.java";
        BufferedReader read = new BufferedReader(new FileReader(filepath));
        String s;
        StringBuffer sb = new StringBuffer();
        while((s=read.readLine()) != null){
            sb.append(s+"
");
        }
        read.close();
        System.out.println(sb);
        
        
        StringReader sr = new StringReader(sb.toString());
        int c;
        while((c=sr.read()) != -1){
            System.out.print((char)c);
        }
    }
}

6. 运行结果如下:

使用BufferedReader读取本地文件的操作

7. 将内容写入文件：

package com.xuzhiwen.io;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.PrintWriter;
import java.io.StringReader;
public class TestBufferedReader {
    public static void main(String[] args) throws Exception {
        String filepath = "src/com/xuzhiwen/io/TargetFile.java";
        BufferedReader read = new BufferedReader(new FileReader(filepath));
        String s;
        StringBuffer sb = new StringBuffer();
        while((s=read.readLine()) != null){
            sb.append(s+"
");
        }
        read.close();
        System.out.println(sb);
        System.out.println("==============================================");
        
        
        StringReader sr = new StringReader(sb.toString());
        int c;
        while((c=sr.read()) != -1){
            System.out.print((char)c);
        }
        sr.close();
        
        System.out.println("==============================================");
        
        String file = "basic.out";
        BufferedReader br = new BufferedReader(new StringReader(sb.toString()));
        PrintWriter pw = new PrintWriter(new BufferedWriter(new FileWriter(file)));
        
        int lineCount = 1;
        String ss;
        while((ss=br.readLine()) != null){
            pw.println(lineCount+":  "+ss);
            lineCount++;
        }
        pw.close();
    }
}