class ClockTime

[Amy Lee]

I've been working on a class called ClockTime where methods are used to carry out various tasks on time. My code is as follows:

public class ClockTime
{   private int[] myTime = new int[3];
    
    public ClockTime()
    {   myTime[0] = 0;
        myTime[1] = 0;
        myTime[2] = 0;
    }
    
    /* pre: hours must be >= 0 and <= 24, minutes must be >= 0 and < 60, seconds must be
     * >= 0 and < 60
     * post: creates a ClockTime object made up of hours, minutes and seconds
     */
    public ClockTime(int hours, int minutes, int seconds)
    {   myTime[0] = hours;
        myTime[1] = minutes;
        myTime[2] = seconds;
    }
    
    /* pre: hours must be >= 0 and <= 24, minutes must be >= 0 and < 60, seconds must be
     * >= 0 and < 60
     * post: returns a string that states whether the two times entered are equal
     */
    public String equals(int h1, int m1, int s1, int h2, int m2, int s2)
    {   int[] t1 = {h1, m1, s1};
        int[] t2 = {h2, m2, s2};
        if( t1.equals(t2) )
        {   return "The two times " + t1[0] + ":" + t1[1] + ":" + t1[2] + " and " + t2[0] + ":" + t2[1] + ":" + t2[2] + " are equal.";
        }
        else
        {   return t1[0] + ":" + t1[1] + ":" + t1[2] + " and " + t2[0] + ":" + t2[1] + ":" + t2[2] + " are NOT equal.";
        }
    }
    
    /* pre: hours must be >= 0 and <= 24, minutes must be >= 0 and < 60, seconds must be
     * >= 0 and < 60
     * post: returns a new time
     */
    public String setTime(int hours, int minutes, int seconds)
    {   int[] newTime = {hours, minutes, seconds};
        myTime = newTime;
        return myTime[0] + ":" + myTime[1] + ":" + myTime[2];
    }
    
    /* pre: none
     * post: returns a string representation of the current time
     */
    public String toString()
    {   return "The time is " + myTime[0] + ":" + myTime[1] + ":" + myTime[2] + ".";
    }
    
    /* pre: hours must be >= 0 and <= 24, minutes must be >= 0 and < 60, seconds must be
     * >= 0 and < 60
     * post: compares object clock to object myTime and returns whether or not myTime
     * occurs before clock
     */
    public boolean before(int hours, int minutes, int seconds)
    {   int[] clock = {hours, minutes, seconds};
        boolean result = true;
        for(int i = 0; i < clock.length && result; ++i)
        {   if(clock[i] < myTime[i])
            {   result = false;
            }
        }
        return result;
    }
}

I'm having problems with method equals() and method before(). When I call method equals(), even if I plug values into each array that make them identical, it is returning the string that they are NOT equal. Same thing happens when I specify values that aren't equal.

When I call method before(), if I use values that make myTime occur before clock, it still returns false. Same thing happens vice versa.

I don't think I'm fully grasping the relationship between arrays and equality. Please help!

THANKS!

[Karthikeyan Rajendraprasad]

there should be a small correction made in the before method

 
if(clock[i] < myTime[i])           
 {   
result = false;            
} 

it should be like

 
if(clock[i] == myTime[i])           
 {   
 continue;            
}
else if(clock[i] < myTime[i])           
 {   
return false;            
}
else
{
  return true;
}
 

in your case it checks the hour first then the minutes and then the seconds. if hour is leeser and minute is greater or vice versa will affect the result. your code will work only if all the values are greater or all the values are less..

[ November 02, 2004: Message edited by: Karthikeyan Rajendraprasad ]
[ November 02, 2004: Message edited by: Karthikeyan Rajendraprasad ]

[Amy Lee]

So then I should get rid of the variable result and the return result statement outside of the for loop, right?

Thanks.

[Karthikeyan Rajendraprasad]

no you cant remove it, if the time is equal you have to return using that variable only. you can either set it as true or false as per your requirement.

[Amy Lee]

Your method works - THANKS! - but I want to understand. I feel like this should be apparent but...

1. boolean result is declared outside the for loop and is initialized to true

2. there are three scenarios in the if statement

3. say the myTime occurs AFTER clock; the if statement will return false - myTime does not occur before clock

4. nowhere in the if statement does it assign the boolean false to result outside the for loop. how does the method know to return result as false if it is never assigned false and it was initialized to true to begin with?

Thanks for your patience.

[Karthikeyan Rajendraprasad]

oops i missed the && result condition in the for loop.

i think you can remove it and set the result as false so the method should look like

public boolean before(int hours, int minutes, int seconds)    
{  
int[] clock = {hours, minutes, seconds};       
boolean result = false;        
for(int i = 0; i < clock.length; ++i)        
{  
if(clock[i] == myTime[i])           
{    
continue;            
}
else if(clock[i] < myTime[i])           
{   
return false;            
}
else
{  
return true;
}     
}        
return result;   
}