Pitfalls and relative path locations encountered when java IO streams read and write files

package 第十章作业;

//要求：把file1.txt里的内容读取在追加写入file2中

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;

public class Test {
public static void main(String[] args) throws Exception { 
    BufferedReader br=new BufferedReader(new FileReader(new File("file1.txt"))); 
    BufferedWriter bw=new BufferedWriter(new FileWriter(new File("file2.txt"),true));
    String line="";
    
    while((line=br.readLine())!=null) {
        bw.write(line);
    }
    br.close();
    bw.close();
}
}

Problems encountered:

1. If your write stream is not closed, your write will be unsuccessful! ! ! ! ! ! ! !

2. The name of the new file is whatever it is. For example, if you create a file named file, when specifying the path for the stream, just write file instead of adding .txt or something like that.