Java - calculate number of pages from size of page and total number of items

In this article, we're going to have a look at how in Java, calculate a number of pages when we know:

• maximal size of the page,
• a total number of items.

Quick solution:

long pageSize = 10;
long totalCount = 21;

long pagesCount = totalCount < pageSize ? 1 : (long) Math.ceil((double) totalCount / pageSize);

Practical example

Simple example:

public class PaginationUtils {

    /**
     * Calculates number of pages for given page size and total number of items.
     *
     * Assumption:
     *     we suppose that if we have 0 items we want 1 empty page
     */
    public static long calculatePagesCount(long pageSize, long totalCount) {

        return totalCount < pageSize ? 1 : (long) Math.ceil((double) totalCount / (double) pageSize);
    }
}

Usage example:

public class Program {

    public static void main(String[] args) {

        long pageSize = 10;
        long totalCount = 21;
        long pagesCount = PaginationUtils.calculatePagesCount(pageSize, totalCount);

        System.out.println("pagesCount=" + pagesCount);  // pagesCount=3
    }
}

Output:

pagesCount=3

The above logic result explanation:

• the total number of items is 21 (totalCount variable),
• the maximal size of the page is 10 items (pageSize variable),

So:

• page 1 should have 10 items
• page 2 should have 10 items
• page 3 should have  1 item

so we have 3 pages.

See also

1. JavaScript - calculate number of pages from size of page and total number of items