Pager.java

package surprise_assignment;


public class Pager {

    private final long totalCount;

    public Pager(long totalCount) {
        this.totalCount = totalCount;
    }

    public String html(long pageIndex) {
        StringBuilder output = new StringBuilder();

        int itemsPerPage = 10;
        long totalPages = (totalCount + itemsPerPage - 1) / itemsPerPage;
        long startPage = ((pageIndex - 1) / itemsPerPage) * itemsPerPage + 1; // 1, 11, 21, 31, ...
        long endPage = Math.min(startPage + itemsPerPage - 1, totalPages);

        output.append("<a href='#'>[처음]</a>").append("\n");

        output.append("<a href='#'>[이전]</a>").append("\n").append("\n");

        for (long i = startPage; i <= endPage; i++) {
            if (i == pageIndex) {
                output.append("<a href='#' class='on'>").append(i).append("</a>").append("\n");
            } else {
                output.append("<a href='#'>").append(i).append("</a>").append("\n");
            }
        }

        if (pageIndex < totalPages) {
            output.append("\n").append("<a href='#'>[다음]</a>").append("\n");
        }

        output.append("<a href='#'>[마지막]</a>");

        return output.toString();
    }

    public static void main(String[] args) {
        long totalCount = 201;
        long pageIndex = 21;

        Pager pager = new Pager(totalCount);
        System.out.println(pager.html(pageIndex));
    }
}