在文件指定行插入一段内容

public class Main {
public static void main(String[] args){
try {
File file1 = new File("src/main/resources/test.txt");
File file2 = new File("src/main/resources/tmp.txt");
BufferedReader br = new BufferedReader(new FileReader(file1));
BufferedWriter bw = new BufferedWriter(new FileWriter(file2));
String line;
int i = 0;
while ((line = br.readLine()) != null){
i++;
if(i != 1){
bw.newLine();
}
bw.write(line);
if (i == 4){
bw.newLine();
bw.write("haha");
}
}
bw.flush();
bw.close();

file2.renameTo(file1);
} catch (IOException e) {
e.printStackTrace();
}
}
}