Could you try to things, just to further test your theory that the
equals is whats failing:
1. Log the value of the key (so the result of key.toString()), just to
see what it is.
2. Do as below:
Test sexKey = new Text("sex");
if(key.equals(sexKey)) {
.
.
}
These 2 should atleast help confirm or deny your theory.
Hope this helps
Tushar
On Sun, Apr 19, 2009 at 9:54 AM, Reza <pdp...@eden.rutgers.edu> wrote:
> Hey Brian:
>
> I tried that as well, but to no avail . =[.
>
> -Reza
>
>> Hm,
>>
>> I don't know how equals() is implemented for Text, but I'd try:
>>
>> key.toString().equals("sex")
>>
>> Brian
>>
>> On Apr 19, 2009, at 11:29 AM, Reza wrote:
>>
>>> Brian:
>>>
>>> Thanks for your response.
>>>
>>> I have 8 total keys and values. The code I show below is part of the
>>> whole
>>> thing, just to illustrate my problem.
>>>
>>> Im trying to call each key with an if statement (as in the piece I
>>> showed
>>> before). Each of my 8 keys have their respective if statement.
>>>
>>> However, it seems that my if statement is not going through. I even
>>> put
>>> the output.collect(...) inside the if statement, and accordingly, no
>>> output was shown. I already tested my mapper, and it seems to work
>>> fine.
>>>
>>> I believe that I am having difficulty at this point:
>>>
>>> if (key.equals("sex")) {...}
>>>
>>> The key in this case is "sex" (or gender) and the possible values
>>> are 0
>>> (for male) and 1 (for female). Is this not the right way to separate
>>> out
>>> my keys?
>>>
>>> -Reza
>>>
>>>> Hey Reza,
>>>>
>>>> From reading your code, you are calling this for the key "sex":
>>>>
>>>> output.collect("The total population is: ", (actual population))
>>>>
>>>> and, for every other key:
>>>>
>>>> output.collect("The total population is: ", 0)
>>>>
>>>> You probably only want to call the output collector in the first
>>>> case,
>>>> not every time.
>>>>
>>>> Brian
>>>>
>>>>
>>>> On Apr 18, 2009, at 12:21 PM, Reza wrote:
>>>>
>>>>> Hello all:
>>>>>
>>>>> I am new to Hadoop and Map Reduce. I am writing a program to analyze
>>>>> some
>>>>> census data.
>>>>>
>>>>> I have a general question with MapReduce:
>>>>>
>>>>> In the Reducer, how can I separate keys to do separate calculations
>>>>> based
>>>>> on the key? In my case, I am trying to use if statements to separate
>>>>> the
>>>>> keys out, but for some reason, it is not doing so.
>>>>>
>>>>> Here is a segment of my code. My mapper seems to work, I think it is
>>>>> my
>>>>> Reducer that is messing up:
>>>>>
>>>>> public static class MapClass extends MapReduceBase implements
>>>>> Mapper<LongWritable, Text, Text, IntWritable> {
>>>>>
>>>>> // private final static IntWritable one = new IntWritable(1);
>>>>> Text sex = new Text("sex");
>>>>> public void map(LongWritable key, Text value,
>>>>> OutputCollector<Text, IntWritable> output,
>>>>> Reporter reporter) throws IOException {
>>>>> String line = value.toString();
>>>>> StringTokenizer itr = new StringTokenizer(line,",");
>>>>>
>>>>> :
>>>>> :
>>>>> word.set(itr.nextToken());
>>>>> IntWritable sexVal = new
>>>>> IntWritable(Integer.parseInt(word.toString())); //map gender
>>>>> output.collect(sex, sexVal);
>>>>>
>>>>> }//end map()method
>>>>> }//end class MapClass
>>>>>
>>>>>
>>>>> public static class Reduce extends MapReduceBase
>>>>> implements Reducer<Text, IntWritable, Text, IntWritable> {
>>>>>
>>>>>
>>>>> public void reduce(Text key, Iterator<IntWritable> values,
>>>>> OutputCollector<Text, IntWritable> output,
>>>>> Reporter reporter) throws IOException {
>>>>>
>>>>> int totalPop = 0; //count: total population
>>>>> int numMales = 0; //count: males
>>>>> int numFemales = 0; //count: females
>>>>> Text popOut = new Text("The total population is:
>>>>> ");
>>>>> if (key.equals("sex")) {
>>>>> while (values.hasNext()) {
>>>>> if (values.next().get() == 0)
>>>>> numMales++; //number
>>>>> of males
>>>>> else
>>>>> numFemales++; //number
>>>>> of
>>>>> females
>>>>> }//end while
>>>>> totalPop = numMales + numFemales; //count of
>>>>> population
>>>>> }//end if
>>>>> output.collect(popOut, new IntWritable(totalPop));
>>>>>
>>>>> }//end reduce method
>>>>> }//end class Reduce
>>>>>
>>>>> key is of type Text, I also used: if (key.toString() == "sex) {....
>>>>> but that wasnt working either.
>>>>>
>>>>> There are of course other keys and values, but I would think to
>>>>> gather all
>>>>> the keys "sex" would be done with the way I show it above. However,
>>>>> My
>>>>> output reads as 0. I tried changing the numMales value to see if
>>>>> the if
>>>>> statement is executed, but it is not. Am I doing something wrong?
>>>>>
>>>>
>>>>
>>
>>
>
>
