Comparing elements in an arraylist

Question

I have to check to see if the "tokens" in the arraylist are in increasing order.

private E[] data;      // where the data is stored   
private int size;      // how many items have been added to the list

public TopSpinArray(int numTokens, int spinSize)
{
    super(numTokens, spinSize);

    data = (E[])(new Object[numTokens]);
    size = 0;
} 

public boolean isSolved()
{     
    for(int i = 0; i < numTokens; i++)
    {
        if(data[i] < data[i+1])
        { 
            return true;
        }
    }
    return false;
}

when I compile, it says "bad operand types for binary operator '<' first type: E; second type: E"

how do I check to see if they are increasing?

Please add the declaration of 'data' - we need to know what type it is if we are to help you. — atk
– atk, Commented Apr 14, 2013 at 20:31
your loop will exit once first element turns out to be less than second. You need to return false once you see elements the other way around. wrt your compilation problem see atk's comment. — akostadinov
– akostadinov, Commented Apr 14, 2013 at 20:33

Keppil · Accepted Answer · 2013-04-14 20:40:26Z

4

The operator < is only valid for certain types of objects. To be able to compare any comparable type of object (I take your E to imply that your tokens indeed implement Comparable, since otherwise your question makes no sense,) you can use compareTo():

for(int i = 0; i < numTokens - 1; i++) {
     if(data[i].compareTo(data[i+1]) > 0) { 
         return false;
     }
}
return true;

edited Apr 14, 2013 at 20:40

answered Apr 14, 2013 at 20:35

Keppil

46.3k9 gold badges101 silver badges121 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Keppil Over a year ago

@awashburn: They should be in ascending order, so if compareTo() returns something > 0, something is wrong.

Collectives™ on Stack Overflow

Comparing elements in an arraylist

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related