Пытаюсь сделать так, но вылетает ошибка.

package com.javarush.task.task18.task1814;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.UnsupportedEncodingException;

/*
UnsupportedFileName
*/

public class TxtInputStream extends FileInputStream {

    public TxtInputStream(FileInputStream fileName) throws IOException {
        super(String.valueOf(fileName));
        if (!fileName.toString().endsWith(".txt")){
            super.close();
            throw new UnsupportedEncodingException();
        }

    }



    public static void main(String[] args)throws IOException{
        TxtInputStream file = new TxtInputStream(new FileInputStream("E:\\3.txt"));
    }
}