输出流读取文件内容转换为图片

package com.gdin.dome;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;

import org.junit.Test;

public class dome5 {

    @Test
    public void fun(){
        try {
        /*
         * 用行为读取的方式，没读取到一行数据就转化为数值
         */
        File file = new File("C:/Users/Administrator/Desktop/test.txt");
        BufferedReader reader = new BufferedReader(new FileReader(file));
        FileOutputStream output = new FileOutputStream(new File("C:/Users/Administrator/Desktop/a.jpg"));
        int i = 0;
        String s = null;//用于保存读取的 字符
        long line = 1l;//每次读取1行
        byte[] b= new byte[1024];
        
            while((s = reader.readLine())!= null){
                
                if(line==1){
                    s = "ff";
                }
                
                i = Integer.parseInt(s, 16);
                output.write(i);
                line++;
                
            }
            reader.close();
            output.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        
    }
}

package com.gdin.dome;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;

import org.junit.Test;

public class dome5 {

@Test
public void fun(){
try {
/*
* 用行为读取的方式，没读取到一行数据就转化为数值
*/
File file = new File("C:/Users/Administrator/Desktop/test.txt");
BufferedReader reader = new BufferedReader(new FileReader(file));
FileOutputStream output = new FileOutputStream(new File("C:/Users/Administrator/Desktop/a.jpg"));
int i = 0;
String s = null;//用于保存读取的 字符
long line = 1l;//每次读取1行
byte[] b= new byte[1024];

while((s = reader.readLine())!= null){

if(line==1){
s = "ff";
}

i = Integer.parseInt(s, 16);
output.write(i);
line++;

}
reader.close();
output.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}
}

从一个txt文件中读取内容，每一行只有一个16进制的编码。但是出现问题就是第一行为不可识别，于是干脆给一行赋值，然后通过输出流输出文件