javacollections

Is there a common Java utility to break a list into batches?


I wrote myself a utility to break a list into batches of given size. I just wanted to know if there is already any apache commons util for this.

public static <T> List<List<T>> getBatches(List<T> collection,int batchSize){
    int i = 0;
    List<List<T>> batches = new ArrayList<List<T>>();
    while(i<collection.size()){
        int nextInc = Math.min(collection.size()-i,batchSize);
        List<T> batch = collection.subList(i,i+nextInc);
        batches.add(batch);
        i = i + nextInc;
    }

    return batches;
}

Please let me know if there any existing utility already for the same.


Solution

  • Check out Lists.partition(java.util.List, int) from Google Guava:

    Returns consecutive sublists of a list, each of the same size (the final list may be smaller). For example, partitioning a list containing [a, b, c, d, e] with a partition size of 3 yields [[a, b, c], [d, e]] -- an outer list containing two inner lists of three and two elements, all in the original order.