Java工程师高薪训练营|十二阶段版

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

public class ListPageUtil<T> {

 
/**
 * 每页显示条数
 */
private int pageSize;
 
/**
 * 总页数
 */
private int pageCount;
 
/**
 * 原集合
 */
private List<T> data;

public ListPageUtil(List<T> data, int pageSize) {
    if (data == null || data.isEmpty()) {
        throw new IllegalArgumentException("data must be not empty!");
    }

    this.data = data;
    this.pageSize = pageSize;
    this.pageCount = data.size()/pageSize;
    if(data.size()%pageSize!=0){
        this.pageCount++;
    }
}

/**
 * 得到分页后的数据
 *
 * @param pageNum 页码
 * @return 分页后结果
 */
public List<T> getPagedList(int pageNum) {
    int fromIndex = (pageNum - 1) * pageSize;
    if (fromIndex >= data.size()) {
        return Collections.emptyList();
    }

    int toIndex = pageNum * pageSize;
    if (toIndex >= data.size()) {
        toIndex = data.size();
    }
    return data.subList(fromIndex, toIndex);
}

public int getPageSize() {
    return pageSize;
}

public List<T> getData() {
    return data;
}

public int getPageCount() {
    return pageCount;
}

public static void main(String[] args) {
    Integer[] array = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};
    List<Integer> list = Arrays.asList(array);

    ListPageUtil<Integer> pager = new ListPageUtil<Integer>(list, 10);
    
    System.out.println(pager.getPageCount());

    List<Integer> page1 = pager.getPagedList(1);
    System.out.println(page1);

    List<Integer> page2 = pager.getPagedList(2);
    System.out.println(page2);

    List<Integer> page3 = pager.getPagedList(3);
    System.out.println(page3);
}

}