paging orders.java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

/**
 * Created by Hung on 4/27/17.
 */
public class ListOperator {

    public static class Order {

        public int orderNumber;

        public Order(int orderNumber) {
            this.orderNumber = orderNumber;
        }


        public String toString() {
            return "Order(" + this.orderNumber + ")";
        }

    }

    public static <T> List<T> getPage(List<T> sourceList, int page, int pageSize) {
        if (pageSize <= 0 || page <= 0) {
            throw new IllegalArgumentException("invalid page size: " + pageSize);
        }

        int fromIndex = (page - 1) * pageSize;
        if (sourceList == null || sourceList.size() < fromIndex) {
            return Collections.emptyList();
        }

        // toIndex exclusive
        return sourceList.subList(fromIndex, Math.min(fromIndex + pageSize, sourceList.size()));
    }


    public static void main(String[] args) {

        List<Order> orders = Arrays.asList(new Order(1), new Order(2), new Order(-1), new Order(-2), new Order(6), new Order(6),
                new Order(10), new Order(11), new Order(12), new Order(100));

        int pageSize = 3; // của em là 100

        int totalPage = orders.size() % pageSize == 0 ? orders.size() / pageSize : orders.size() / pageSize + orders.size() % pageSize;

        System.out.println(totalPage);


        for (int i = 1; i <= totalPage; i++) {
            List<Order> page = getPage(orders, i, pageSize);
            ArrayList<Order> results = new ArrayList<>();
            for (Order order : page) {
                if (order.orderNumber > 0) {
                    results.add(order);
                }
            }
            System.out.println(results);
        }
    }
}