Hola, en este programa, que funcion cumple hashcode?, por que el hashcode se calcula con la numeración 17 y 31?, para calcular el metodo hashcode debo seguir alguna numeracion especial o en base a que cosa debo calcularlo
gracias
Código PHP:
public final class PhoneNumber
{
private final short areaCode;
private final short prefix;
private final short lineNumber;
public PhoneNumber(int areaCode, int prefix,int lineNumber)
{
rangeCheck(areaCode, 999, "area code");
rangeCheck(prefix, 999, "prefix");
rangeCheck(lineNumber, 9999, "line number");
this.areaCode = (short) areaCode;
this.prefix = (short) prefix;
this.lineNumber = (short) lineNumber;
}
private static void rangeCheck(int arg, int max,
String name) {
if (arg < 0 || arg > max)
throw new IllegalArgumentException(name +": " + arg);
}
@Override public boolean equals(Object o)
{
if (o == this)
return true;
if (!(o instanceof PhoneNumber))
return false;
PhoneNumber pn = (PhoneNumber)o;
return pn.lineNumber == lineNumber
&& pn.prefix == prefix
&& pn.areaCode == areaCode;
}
@Override public int hashCode() {
int result = 17;
result = 31 * result + areaCode;
result = 31 * result + prefix;
result = 31 * result + lineNumber;
return result;
}
public String toString()
{
return "("+areaCode+"-"+prefix+"-"+lineNumber+")";
}
public static void main(String arguments[])
{
PhoneNumber po= new PhoneNumber(5,222,4);
System.out.println(po);
}}