Re: List.contains problem

> Rick,
>
> Ok. I see.  I was hoping that as long as two Options's lable and value are
> same, they are treated as equal. But I guess, not the case.
>
> Looks like the contains method is not very useful at all. B/c most of time,
> you have to loop throught to find it out if there's another one already in
> the list.
>
> Thanks and have a good day.
> Jimmy
>
>
> Rick Fincher wrote:
>  
>> Hi Jimmy,
>>
>> The contains() method just loops through the list and checks to see if
>> any of the objects in the list are the same object as the one you pass
>> in through the contains() method.
>>
>> By "the same" I mean actually the same, not just one that has the same
>> entries for label and value, but physically the very same option object.
>>
>> If you are trying to see if an option with the same label and same value
>> is already in there, you can get an iterator and loop through quickly,
>> as in:
>>
>> ArrayList<Option> opt = new ArrayList<Option>();
>>        
>>         Iterator<Option> optIt = opt.iterator();
>>         boolean duplicateFound = false;
>>        
>>         while (optIt.hasNext()) {
>>             if ( (optIt.next().getValue().toString().equals
>> (testOpt.value()).toString()) &&  
>> (optIt.next().getLabel().equals(testOpt.label())) ) {
>>                 duplicateFound = true;
>>             }
>>         }
>>
>> You can make that a method that returns a boolean to make it a little
>> cleaner if you like.  This is assuming that the toString() method for
>> the value is meaningful.  If the value is something else, ubstitute the
>> appropriate comparison.
>>
>> The label is already a String so you don't have to use toString().
>>
>>
>> Rick
>>
>> Jimmy200012 wrote:
>>    
>>> Rick,
>>>
>>> Thank you so much for the quick reply. So, is there any quick way to
>>> check
>>> if a new Option is in the Option Array []? Do I have to loop through to
>>> find
>>> out? So what's the contians method for?
>>>
>>> Thanks again!
>>> Jimmy
>>>
>>>
>>> Rick Fincher wrote:
>>>  
>>>      
>>>> Hi Jimmy,
>>>>
>>>> This does not work because testOpt and MyOpt[0] are two different
>>>> objects, even though their labels and values are the same.  If your code
>>>> was the following it would work:
>>>>
>>>> Option testOpt = new Option("R2", "R2");
>>>>
>>>> Option[] myOpt = new Option[]{
>>>>             testOpt,
>>>>             new Option("L22", "L2")
>>>>         };
>>>>
>>>> The equals(0 method compares pointers to the object.  For Strings this
>>>> works because Strings are immutable values and only one copy of a String
>>>> containing the same characters is stored in memory.
>>>>
>>>> If you do code like this:
>>>>
>>>> String s1="hello";
>>>> String s2="hello";
>>>>
>>>> Only one copy of the String "hello" is stored in memory with both s1 and
>>>> s2 pointing to it.  If you do this later:
>>>>
>>>> s2="goodby";
>>>>
>>>> A new String "goodby" is created and s2 is set to point to it, unless
>>>> "goodby" was already in memory, then s2 would be set to point to the
>>>> pre-existing String "goodby".
>>>>
>>>> Because of that the String method equals() will work in situations like
>>>> this.
>>>>
>>>> That's one of the reasons String methods are slow in Java.  Every time
>>>> you
>>>> change it a new String is created and the old one is left for garbage
>>>> collection.
>>>>
>>>> Manipulating StringBuffers is much faster and more memory efficient.
>>>>
>>>> Rick
>>>>
>>>>
>>>> Jimmy200012 wrote:
>>>>    
>>>>        
>>>>> Hi, need some help to understand why this won't work:
>>>>>
>>>>> import com.sun.webui.jsf.model.Option;
>>>>> import java.util.*;
>>>>>
>>>>> public class ArrayListContains {
>>>>>
>>>>>     /** Create a new instance of ArrayListContains */
>>>>>     public ArrayListContains() {
>>>>>     }
>>>>>
>>>>>     public static void main(String[] args) {
>>>>>         // Now the real test;
>>>>>         Option[] myOpt = new Option[]{
>>>>>             new Option("R2", "R2"),
>>>>>             new Option("L22", "L2")
>>>>>         };
>>>>>
>>>>>         Option testOpt = new Option("R2", "R2");
>>>>>
>>>>>         ArrayList<Option> optList = new
>>>>> ArrayList<Option>(Arrays.asList(myOpt));
>>>>>         if (optList.contains(testOpt)) {
>>>>>
>>>>>             // YOU THOUGHT WOULD PRINT THIS, BUT NOT.
>>>>>             // com.sun.webui.jsf.model.Option DID NOT IMPLEMENTS
>>>>> EQUALS?
>>>>>             // WHERE CAN I FIND SOME DOC ABOUT THIS?
>>>>>             System.out.println("Yes!!!!!!!!!!!!R2");
>>>>>         } else {
>>>>>             System.out.println("why?????????????");
>>>>>         }
>>>>>     }
>>>>> }
>>>>>  
>>>>>      
>>>>>          
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>>>>
>>>>    
>>>>        
>>>  
>>>      
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>>    
>
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