Code Explanation

1-

} catch (FileNotFoundException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
}

This code is part of a try catch statement. This instruction is used to catch exceptions and thus avoid an inappropriate behavior of our program. You can specify the type of exception you want to catch, in this case FileNotFoundException (happens if the file we are referring to cannot be found) and IOException (happens when we have a problem when reading or writing).

An exception can be caught without indicating the type of exception, doing so in a general way with Exception.

http://leo.ugr.es/J2ME/CLDC/transjava/node10.html

two-

public String toString() {
return (getNombre() + " " + getP_Apellido() + " "
        + getS_Apellido());

}

Definition of the method toString(); All objects have a toStrnig method defined. What has been done here is to redefine it so that, when called, it returns a string made up of a first name last name last name. This is usually done when we create a custom object, to return whatever we want.

3-

public static void main(String[] args) {
Employee e = new Employee();   //Creamos un objeto del tipo Empleado
e.name = "Reyan Ali";          //Damos valor a sus atributos
e.address = "Phokka Kuan, Ambehta Peer";    //Damos valor a sus atributos
e.SSN = 11122333;     //Damos valor a sus atributos
e.number = 101;    //Damos valor a sus atributos

try {
    FileOutputStream fileOut
            = new FileOutputStream("employee.ser");  //Creamos un objeto que apunte al fichero employee.ser
    ObjectOutputStream out = new ObjectOutputStream(fileOut);  //Creamos un objeto para escribir en el fichero
    out.writeObject(e);   //Escribimos el objeto empleado en el fichero
    out.close();    //Cerramos el objeto para escribir
    fileOut.close();  //Cerrramos el objeto que apunta al fichero
    System.out.printf("Serialized data is saved in /employee.ser");  //Imprimimos por pantalla el mensaje Serialized data...
} catch (IOException i) {   //Capturamos la excepción si hay algún problema
    i.printStackTrace();   //Mostramos el mensaje de la excepción
}
}

4-

public void mailCheck() {
    System.out.println("Mailing a check to " + name + " " + address);
}

The mailCheck method is defined, which what it does is paint the Mailing check to name address message on the screen, replacing name and address with their corresponding values

5-

Employee e = null;
try {
    FileInputStream fileIn = new FileInputStream("employee.ser");
    ObjectInputStream in = new ObjectInputStream(fileIn);
    e = (Employee) in.readObject();
    in.close();
    fileIn.close();
} catch (IOException i) {
    i.printStackTrace();
    return;
} catch (ClassNotFoundException c) {
    System.out.println("Employee class not found");
    c.printStackTrace();
    return;
}
System.out.println("Deserialized Employee...");
System.out.println("Name: " + e.name);
System.out.println("Address: " + e.address);
System.out.println("SSN: " + e.SSN);
System.out.println("Number: " + e.number);
}

This part of code is explained with what was said in the previous ones.