Exception in thread "main" java.lang.NoClassDefFoundError problema

[ROCCHEFILI]

qui le classi:

package Eventoaula;
public class Evento {

    private int giorno;
    private int ora;
    private int durata;
    
    public Evento (int a, int b, int c){
        giorno=a;
        ora=b;
        durata=c;
    }
    
    public boolean Inserisco(Evento e){
        int dpe=this.ora+this.durata;
        int dse=e.ora+e.durata;
        boolean b=true;
        if (this.giorno==e.giorno){
            if(dpe>=e.ora || dse<=this.ora)
                b=false;
        }
        return b;
        }

seconda classe:

package Eventoaula;
import java.util.*;
import java.io.*;
public class Esercizio1 {
 public static void main (String [] args) throws IOException {

 
 ArrayList <Evento> R = new ArrayList <Evento>();
 File ff = new File (args [1]); 
 Scanner sc = new Scanner (ff);