Notes

public class Call
{
private String number;
private CallZone zone;
private int minutes;

/**
* Create a call with the given number, call zone, and number of minutes.
*
* @param number the call's number.
* @param zone the call's call zone.
* @param minutes the call's duration in minutes.
* @pre. minutes is positive and number and zone are not null.
*/
public Call(String number, CallZone zone, int minutes)
{
assert(minutes > 0);
this.setNumber(number);
this.setZone(zone);
this.setMinutes(minutes);
}

/**
* Make a copy of the given call.
*
* @param call the call to make a copy of.
* @pre. call is not null.
*/
public Call(Call call)
{
this(call.getNumber(),call.getZone(),call.getMinutes());
}

/**
* Get the number of this call.
*
* @return the number of this call.
*/
public String getNumber()
{
return this.number;
}

/**
* Set the number of this call.
*
* @param number the number to set.
* @pre. number is not null.
*/
public void setNumber(String number)
{
this.number = number;
}

/**
* Get the zone of this call.
*
* @return the zone of this call.
*/
public CallZone getZone()
{
return this.zone;
}

/**
* Set the zone of this call.
*
* @param zone the zone to set.
* @pre. zone is not null.
*/
public void setZone(CallZone zone)
{
this.zone = zone;
}

/**
* Get the minutes of this call.
*
* @return the minutes of this call.
*/
public int getMinutes()
{
return this.minutes;
}
/**
* Set the number of minutes of this call.
*
* @param minutes the number of minutes to set
* @pre. minutes is positive.
*/
public void setMinutes(int minutes)
{
assert minutes > 0;
this.minutes = minutes;
}

/**
* Creates a string representation of the object.
* The string includes the number, call zone, and
* number of minutes of the call. For example,
* "call to number +14167362100 in zone CANDA for 12 minutes".
*
* @return the string representation of the object.
*/
@Override
public String toString()
{
return "call to number " + this.getNumber() + " in zone " + this.getZone() + " for " + this.getMinutes() + " minutes";
}

/**
* Creates a hash code for the object.
* The hash code is generated by considering the call's number, call zone, and number of minutes.
*
* @return the object's hash code.
*/
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + minutes;
result = prime * result + ((number == null) ? 0 : number.hashCode());
result = prime * result + ((zone == null) ? 0 : zone.hashCode());
return result;
}

/**
* Indicates whether some other object is "equal to" this one.
* The result is true if and only if the argument is not null, is a call,
* and both objects have the same number, call zone, and number of minutes.
*
* @param obj the object to compare with.
* @return true if the calls' number, call zone, and number of minutes are equal; false otherwise.
*/
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
Call other = (Call) obj;
if (minutes != other.minutes)
return false;
if (number == null) {
if (other.number != null)
return false;
} else if (!number.equals(other.number))
return false;
if (zone == null) {
if (other.zone != null)
return false;
} else if (!zone.equals(other.zone))
return false;
return true;
}
}