java, try-resourses block demo -> unreportedException java.io.IOException

$ cat Main.java

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class Main {
    public static void main(String...args) {
        TryResoursesDemo.copyFile(args[0], args[1]);
    }
}

class TryResoursesDemo {
    public static void copyFile(String fileFrom, String fileTo) {
        try (FileInputStream fin = new FileInputStream(fileFrom);
             FileOutputStream fout  = new FileOutputStream(fileTo);
        ) {
            int ch;
            while ((ch = fin.read()) != -1) {
                fout.write(ch);
            }
            System.out.println("file has been copyied.");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

$ javac Main.java

$ java Main Main.java Main.txt
file has been copied.

$ 

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class Demo {
    public static void main(String...args) throws IOException {
        Demo.tryResoursesDemo("one", "two");
    }

    public static void tryResoursesDemo(String fileFrom, String fileTo) {
        try (FileInputStream fin = new FileInputStream(fileFrom);
             FileOutputStream fout = new FileOutputStream(fileTo);
        ){
            int ch;
            while( (ch = fin.read()) != -1) {
                fout.write(ch);
            }
            System.out.println("copyied");
        }
    }
}

Demo.java:11: error: unreported exception FileNotFoundException; must be caught or declared to be thrown
        try (FileInputStream fin = new FileInputStream(fileFrom);
                                   ^
Demo.java:12: error: unreported exception FileNotFoundException; must be caught or declared to be thrown
             FileOutputStream fout = new FileOutputStream(fileTo);
                                     ^
Demo.java:11: error: unreported exception IOException; must be caught or declared to be thrown
        try (FileInputStream fin = new FileInputStream(fileFrom);
                             ^
  exception thrown from implicit call to close() on resource variable 'fin'
Demo.java:12: error: unreported exception IOException; must be caught or declared to be thrown
             FileOutputStream fout = new FileOutputStream(fileTo);
                              ^
  exception thrown from implicit call to close() on resource variable 'fout'
Demo.java:15: error: unreported exception IOException; must be caught or declared to be thrown
            while( (ch = fin.read()) != -1) {
                                 ^
Demo.java:16: error: unreported exception IOException; must be caught or declared to be thrown
                fout.write(ch);
                          ^
6 errors

try (FileInputStream fin = new FileInputStream(fileFrom);
             FileOutputStream fout  = new FileOutputStream(fileTo);
        ) {
            int ch;
            while ((ch = fin.read()) != -1) {
                fout.write(ch);
            }
            System.out.println("file has been copyied.");
        } catch (IOException e) {
            e.printStackTrace();
        }

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class Main {
    public static void main(String...args) {
        try {
           TryResoursesDemo.copyFile(args[0], args[1]);
        } catch (IOException e) {
           e.printStackTrace();
        }
    }
}

class TryResoursesDemo {
    public static void copyFile(String fileFrom, String fileTo) 
      throws IOException {
        try (FileInputStream fin = new FileInputStream(fileFrom);
             FileOutputStream fout  = new FileOutputStream(fileTo);
        ) {
            int ch;
            while ((ch = fin.read()) != -1) {
                fout.write(ch);
            }
            System.out.println("file has been copyied.");
        } 
    }
}