1.新建目標類：

package com.xuzhiwen.io;

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

2.測試類：

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
 
+"\n");
        }
        read.close();
        System.out.println(sb);
    }
}

3.輸出結果為：

4.文件結構樹：

5. 將結果用StringReader再讀一次：

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+"\n");
        }
        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. 運行結果如下:

7. 將內容寫入文件：

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+"\n");
        }
        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();
    }
}

8. 運行結果：

9. 打開： basic.out文件：

BufferedReader 讀取文件內容，原樣輸出