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  1. #1
    alan117 is offline Member
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    Default counting element(s) appearance(s) in arrays

    Hi all
    I need some help please with Java and arrays.
    I have two arrays: customerID and transactionValue (they are pairs so each transaction has a customer ID and a customer may have made several transactions).
    The number of elements in each array has an int variable called ‘size’.

    I need to work out, and display( using loops and ‘if’ statements): for each customer I need to display the number of transactions that are on the list.
    So I thought I could use variable (int for customer ID and double for transaction values) to “go through the array and count the number of times that for example customer 0 is represented, when that is done do the loop again and see how many times customer 1 is represented and so on”.
    This is my initial thoughts but I may be totally wrong, and clearly I need more code:
    int count=0;
    int thisValue;

    for (index=0;index<size;index++){

    for (thisValue=0;thisValue<size;thisValue++){

    if (customerID[index]==thisValue){

    count=count++;
    }

    }

    }

    System.out.println ("The count is= "+count);
    }






    The final output must look something like this:

    Customer ID Transaction Value
    2, 45.2
    1, 55.2
    3, 10.3
    3, 20
    0, 400.2
    4, 100.30
    3, 50.5

    Customer: 2, Transactions:1
    Customer: 1, Transactions: 1
    Customer: 3, Transactions 3
    Customer: 0, Transactons: 1
    Customer: 4, Transactions: 1

    I have been struggling for hours so any pointers would be most welcome- thanks

  2. #2
    mine0926 is offline Senior Member
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    Default Re: counting element(s) appearance(s) in arrays

    Welcome, please use code tags when posting codes.
    Can you show the output when you run your code?

  3. #3
    alan117 is offline Member
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    Default Re: counting element(s) appearance(s) in arrays

    thank mine0926, umm I'm not sure how to use code tags but I'll try next time.
    the output that I have managed to produce is the customerID and the TransactionValue pair, so I can produce this:
    Customer ID Transaction Value
    2, 45.2
    1, 55.2
    3, 10.3
    3, 20
    0, 400.2
    4, 100.30
    3, 50.5

    Now I need to be able to sort though the above and print out how many times cutomerer 0 has a transaction, how many times customer1 has a transaction and so on.
    Can you help with that bit of the problem?

  4. #4
    DarrylBurke's Avatar
    DarrylBurke is offline Forum Police
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    Default Re: counting element(s) appearance(s) in arrays

    Quote Originally Posted by alan117 View Post
    I'm not sure how to use code tags but I'll try next time.
    BB Code List - Java Programming Forum

    db
    If you're forever cleaning cobwebs, it's time to get rid of the spiders.

  5. #5
    alan117 is offline Member
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    Default Re: counting element(s) appearance(s) in arrays

    mine0926 and Darryl
    Thanks for your comments.
    Here is the code below with code tags.

    At present if I run this code I get 0 printed out.
    If I set the value of count to 1 I get 1 printed out.

    So it does not seem to be counting!

    Can you see where I am going wrong?


    Java Code:
     int count=0;
    	int thisValue;
    	
    	for (index=0;index<size;index++){
    	count=0;
    
    
    	for (thisValue=0;thisValue<size;thisValue++){
    
    	if (customerID[index]==customerID[thisValue]){
    
    	count=count++;
    
    
    
    	}
    	
    
    	}
    	
    	System.out.println ("counter=  "+count);
    	}
    
    	//System.out.println ("counter= "+count);
    }
    With the above code I can produce this output:
    C:\ass3>java As
    CustomerID, Transaction Value
    3 30.31
    2 13.21
    0 23.09
    3 48.58
    1 4.12
    4 38.53
    2 8.83
    2 9.3
    4 85.21
    2 72.34
    customer:3, 0
    customer:2, 0
    customer:0, 0
    customer:3, 0
    customer:1, 0
    customer:4, 0
    customer:2, 0
    customer:2, 0
    customer:4, 0
    customer:2, 0
    Last edited by alan117; 08-19-2012 at 09:30 AM. Reason: add output

  6. #6
    Norm's Avatar
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    Default Re: counting element(s) appearance(s) in arrays

    Also posted at Counting element(s) appearance(s) in arrays
    and
    Counting element(s) in array(s) - Dev Shed

    @OP Please tell us where the same question is on other forums so we don't waste time working on a solved problem.
    If you don't understand my response, don't ignore it, ask a question.

  7. #7
    mine0926 is offline Senior Member
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    Default Re: counting element(s) appearance(s) in arrays

    First, please tell us if you posted this question in other forums.
    Second, please practice indention in your code.. I edit you code and put indent properly
    Java Code:
            int count;
            int thisValue;
    
            for (index=0;index< size;index++)
            {
                count=0;
                for (thisValue=0;thisValue<size;thisValue++)
                {
                    if (customerID[index]==customerID[thisValue])
                    {
                        count=count++;
                    }
                }
                System.out.println ("counter=  "+count);
            }
    On your problem, it might be useful if you put some System.out.println() so you can see why your program returns zero like this
    Java Code:
            int count;
            int thisValue;
    
            for (index=0;index< size;index++)
            {
                count=0;
                System.out.println("customerID[index] " + customerID[index]);            
                for (thisValue=0;thisValue<size;thisValue++)
                {
                    System.out.println("customerID[thisValue] " + customerID[thisValue]);            
                    if (customerID[index]==customerID[thisValue])
                    {
                        count=count++;
                    }
                }
                System.out.println ("counter=  "+count);
            }

  8. #8
    mine0926 is offline Senior Member
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    Default Re: counting element(s) appearance(s) in arrays

    another thing is you put count=count++
    i++ and i=i++ have different result. try it so you can see.

  9. #9
    alan117 is offline Member
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    Default Re: counting element(s) appearance(s) in arrays

    Sorry about the multiple postings, I guess I should have realised people might belong to multiple forums.
    I was looking for advice and thought the more exposure I got, the more opinions I might receive.
    I appreciate your help and suggestions and certainly did not mean to waste your time by posting in several forums.
    Cheers

  10. #10
    JosAH's Avatar
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    Default Re: counting element(s) appearance(s) in arrays

    Quote Originally Posted by alan117 View Post
    clearly I need more code
    No you don't; you need to take a serious look at the Map<T, U> interface and the Collections framework in general. All that array fiddling is so Fortranesque ...

    kind regards,

    Jos
    The only person who got everything done by Friday was Robinson Crusoe.

  11. #11
    Norm's Avatar
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    Default Re: counting element(s) appearance(s) in arrays

    I think the assignment precludes using other classes. It's purpose is to teach array searching and using loops.
    If you don't understand my response, don't ignore it, ask a question.

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