# Collapse Java SequenceIterator Methods

> The collapse Java SequenceIterator methods operate on the object's and the input sequences, left and right, to produce the computed scalar result of type `double`.

> The method signatures are of the following form (where `op` is the indicated operation):

>         public SequenceIterator op(SequenceIterator weights)

> The following table lists the available collapse methods:

> `public SequenceIterator wsum(SequenceIterator weights)` | Calculate the weighted sum of the two sequences
> `public SequenceIterator wavg(SequenceIterator weights)` | Calculate the weighted average of the two sequences
> `public SequenceIterator cov(SequenceIterator other)` | Calculate the covariance of the two sequences
> `public SequenceIterator corr(SequenceIterator other)` | Calculate the correlation of the two sequences

> ## Example

> Following is an example code snippet demonstrating a collapse function:

>         {
>             ...
>             SequenceIterator high = quote.high.iterator();
>             SequenceIterator low = quote.low.iterator();

>             // Calculate the correlation between low and high
>             SequenceIterator  corr =  low.corr(high);
>             ...
>             }
>         }