Thread: Help with ArrayList ( Adding certain elements together)

I also wanted to know how to convert an object to an int.

The only sure way is to use Object.hashCode(), but perhaps you're not asking the right question.

It depends on what the Object is. If the Object is a java.lang.Integer, then there's a handy method that'll get you an int. If the Object is a java.lang.String, you may still use a method from java.lang.Integer (look in the API docs), but you should probably also validate your String first. Try to be more specific.

Ok to put things alittle more clear, ill post some code.

 
ArrayList tal = new ArrayList();
FileInputStream fstream = new FileInputStream("chinese.txt");
DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String strLine
while ((strLine = br.readLine()) != null)
{
 tal.add(strLine);
}
for (int i=0;i<tal.size();i++)
{
system.out.println(tal.get(i));
}

Basically afterwards i will i will have values in lines 1-20 which is 0-19.

Suppose i want to add tal.get(1) and tal.get(2) and store that added value into another variable, what will i have to do? The number inside the file chinese.txt is random numbers, lets say its 5 and 6 so the added value would be 11.

The number inside the file chinese.txt is random numbers

strLine = br.readLine()

You're reading Strings from the file. If you want to store / manipulate numbers, you should be converting each String you read from your input to a number. If the numbers are integer, then java.lang.Integer has a method to convert String to int. If the numbers are not integers, then you may need to use java.lang.Float, java.lang.Double or even java.math.BigDecimal. If the numbers are decorated in any way (such as "£2,045.67") than you'll need to use something that 'understands' funny formats such as (possibly - I've never used it) the 'parse' method in java.text.DecimalFormat

Is it possible you can give me some code to help me our so what should i do, do that line, then convert each line to int, then i am able to add them?

Originally Posted by williamsant

Is it possible you can give me some code to help me our so what should i do, do that line, then convert each line to int, then i am able to add them?

See Integer (Java Platform SE 7 )

Ok i figured it out, what i wanted to ask also is i wanted to create a simple GUI with that program, and display the values in a textbox of some sort, also a simple one. Any suggestions?

That's a different problem, so I'd say you should have a new thread. Why aren't you using BigInteger for your problem?

Thanks Sean4u, Is there a way to move it or is it just a case of delete it here and start it again?

N.B. I'm not using BigInteger because up until this moment I had never heard of it!

Is there a way to move it

I think I've seen it happen, so maybe there is. I might even (unbeknownst to me) have the power to do it myself, though I tend to be better at theory than implementation.

Your loop-of-loops should work, but I would look at this problem and see *intermediate results*. The product of the second 5 integers is the product of the last four (from the result before) and the sixth element in the list. Instead of potentially multiplying each element 5 times, you could 'slide a 5 element window' over the list, doing something appropriate with the element that falls out of the trailing edge of the window and something appropriate with the element that slides under the leading edge of the window.

It's pencil and old envelope time!

Genius idea... as you have undoubtably guest I'm a java newbie so the practical implementation of such a windo might be out of my imediate reach but I love the idea and will see were it takes me.

Im just going to try and move this post before continuing however having looked around I think that only forum moderators can move posts!

ok I've moved over to here:

http://www.javaprogrammingforums.com...html#post44016