How two objects can be equal

[Venkat Ramsimha]

Hi All,
can anybody say how can the two objects be equal?is it true to say if two references point to same object can the two objects be equal?
can any body provide a sample program for this to illustrate

Thanks
venkat ram simha

[Edwin Dalorzo]

package ranch;
 
import java.io.PrintStream;
 
public class Equality{
 
private static final PrintStream out = System.out;
 
public static void main(String args[]){
PhoneNumber aNumber = new PhoneNumber(336,7714556);
PhoneNumber bNumber = new PhoneNumber(506,2688883);
PhoneNumber cNumber = new PhoneNumber(336,7714556);

out.println("aNumber.equals(bNumber): "+aNumber.equals(bNumber));
out.println("aNumber.equals(cNumber): "+aNumber.equals(cNumber));

out.println("aNumber.compareTo(bNumber): "+aNumber.compareTo(bNumber));
out.println("aNumber.compareTo(cNumber): "+aNumber.compareTo(cNumber));
out.println("aNumber.compareTo(aNumber): "+aNumber.compareTo(aNumber));

out.println("aNumber.hashCode(): "+aNumber.hashCode());
out.println("bNumber.hashCode(): "+bNumber.hashCode());
out.println("cNumber.hashCode(): "+cNumber.hashCode());


}
 
}
 
class PhoneNumber implements Comparable{
private int code;
private long number;


public PhoneNumber(int code,long number){
this.code = code;
this.number = number;
}

//Overriden equals method, so that two phone number are equal
public boolean equals(Object o){
if (!(o instanceof PhoneNumber))
return false;

PhoneNumber toBeCompared = (PhoneNumber) o;
return (this.code == toBeCompared.code && this.number == toBeCompared.number) ;
}


//If two equal phone numbers are compared, the result is 0 if they are equal
public int compareTo(Object o){
PhoneNumber toBeCompared = (PhoneNumber) o;

if(this.code > toBeCompared.code)
return 1;
else if(this.code < toBeCompared.code)
return -1;
else if (this.number > toBeCompared.number)
return 1;
else if(this.number < toBeCompared.number)
return -1;
else
return 0;
}


//It is a good practice that if you override equals you override hashCode, so that if two Phonumbers are
//equal, they have the same hash code.
public int hashCode(){
int result = 17;

result = 37*result + code;
result = 37*result + (int) number;

return result;
}


}

[ April 30, 2005: Message edited by: Edwin Dalorzo ]

[Alex Belisle Turcot]

venkatramsimha, you are like an automatic posting machine...
[ April 30, 2005: Message edited by: Alex Turcot ]