List 分頁截斷工具類

package com.inco.core.util;

import com.inco.entity.pub.pub.Dbb;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

/**
 * List 分頁截斷工具類
 * @author dingqiming
 * @Date: 2019-12-18 16:47
 * @param <T>
 */
public class ListSplitIterator<T> implements Iterator<List<T>> {
    protected List<T> originData;
    private int position;
    //默認每頁 1000 條
    private int pageSize = 1000;

    public ListSplitIterator(List<T> originData) {
        if (originData == null) {
            return;
        }
        this.originData = originData;
        position = 0;       //初始化位置爲 0
    }

    public ListSplitIterator(List<T> originData, int pageSize) {
        this(originData);
        if (pageSize <= 0) {
            throw new IllegalArgumentException("pageSize 需要輸入一個大於 0 的值");
        }
        this.pageSize = pageSize;
    }

    @Override
    public boolean hasNext() {
        return originData != null && !originData.isEmpty() && position < originData.size();
    }

    @Override
    public List<T> next() {
        if (hasNext()) {
            int start = position;
            int end = position + pageSize;
            if (end >= originData.size()) {
                end = originData.size();
            }
            List<T> current = originData.subList(start, end);
            position = end;
            return current;
        }
        return null;
    }

    @Override
    public void remove() {
        throw new RuntimeException("未實現 remove 方法");
    }

    public int size() {
        return originData == null ? 0 : (originData.size() - 1) / pageSize + 1;
    }

    public List<T> get(int index) {
        if (originData == null) return null;

        int start = index * pageSize;
        int end = (index + 1) * pageSize;
        if (end >= originData.size()) {
            end = originData.size();
        }
        return originData.subList(start, end);
    }

    /**
     * 獲取當前位置
     *
     * @return
     */
    public long position() {
        return position;
    }

    /**
     * 使用方法
     * @param args
     */
    public static void main(String[]args){
        // 獲取數據
        List<Dbb> batches = new ArrayList();
        // 每批數據的大小
        int batchCount = 500;
        // 構建分割
        ListSplitIterator<Dbb> batchListSplitIterator = new ListSplitIterator<>(batches, batchCount);
            // 迭代每一批數據
        while (batchListSplitIterator.hasNext()){
            List<Dbb> batchSubList = batchListSplitIterator.next();
        }
    }
}