자바 파일 입출력 질문드려요

import java.util.StringTokenizer;
import java.io.*;
 
class JAVA_File {
 
public static void main(String[] args){
	try{
			File imsifile = new File("./file_pra/data2.txt");
		String s = "캐릭터 정보";
		String k;
 
			BufferedReader an = new BufferedReader(new FileReader(imsifile));
 
		File filename = new File("./file_pra/data.txt");
		BufferedReader ow = new BufferedReader(new FileReader(filename));
 
		System.out.println(ow.readLine());
		k=ow.readLine();	
		if(k==""){
			BufferedWriter wr = new BufferedWriter(new FileWriter("./file_pra/data.txt"));
			System.out.println(ow.readLine());
			wr.write(s);
			wr.newLine();
			wr.close();
		}
		else{
			BufferedWriter ir = new BufferedWriter(new FileWriter(imsifile));
			do{
				ir.write(ow.readLine());
				ir.newLine();
			}while(ow.readLine()!=null);
			ir.write(s);
			ir.close();
			BufferedWriter wr = new BufferedWriter(new FileWriter("./file_pra/data.txt"));
			do{
				wr.write(an.readLine());
				wr.newLine();
			}while(an.readLine()!=null);
				wr.close();
		}
 
	}catch(Exception ex){
		ex.printStackTrace();
	}
	}
}