Java 对两个list的对比操作工具类

        目前在项目中遇到如下的需求，在项目中有一个定时任务去统计数据，统计出来的数据会存入一张统计表A中，每次统计的时候需要去判断新旧统计数据（两个List），如果原来已经存在的数据进行更新，原来不存在的数据进行新增，原来存在但是新数据中不存在的数据进行删除。于是进行了架构设计，通过使用一个抽象类和一个新旧数据对比处理类来实现这一需求。

        抽象类代码如下：

public abstract class HomeReportDataBuilder<T> {
	 /**
     * Render the hash code of operation.
     * <p>
     * Example: (companyId_serviceId_operation_recordId).hashCode()
     * </p>
     * 
     * @param t
     * @return
     */
    public String renderKey(T t) {
        return null;
    }
    
    /**
     * Render the hash code of operation.
     * <p>
     * Example: (companyId_新旧数据对比处理类serviceId_operation_recordId).hashCode()
     * </p>
     * 
     * @param t
     * @return
     */
    public String renderUpdateIbatis() {
        return null;
    }
    
    /**
     * Render the hash code of operation.
     * <p>
     * Example: (companyId_serviceId_operation_recordId).hashCode()
     * </p>
     * 
     * @param t
     * @return
     */
    public String renderAddIbatis() {
        return null;
    }
    
    /**
     * Render the hash code of operation.
     * <p>
     * Example: (companyId_serviceId_operation_recordId).hashCode()
     * </p>
     * 
     * @param t
     * @return
     */
    public String renderDeleteIbatis() {
        return null;
    }
}

        新旧数据对比处理类代码如下：

public class HomeReportServiceImpl implements HomeReportService {
	protected BatchDao batchDao;

	public BatchDao getBatchDao() {
		return batchDao;
	}

	public void setBatchDao(BatchDao batchDao) {
		this.batchDao = batchDao;
	}

	public <T extends BaseEntity> void dealData(Map<String, T> currentData, List<T> originalData, HomeReportDataBuilder<T> dataBuilder) {
		List<T> updateList = new ArrayList<T>();
		List<T> addList = new ArrayList<T>();
		List<T> deleteList = new ArrayList<T>();

		// separate currentData and originalData to updateList, addList and deleteList

		for (T originalItem : originalData) {
			String key = dataBuilder.renderKey(originalItem);
			// this originalItem has data today, we will update data
			if (currentData.containsKey(key)) {
				T current = currentData.get(key);
				current.setId(originalItem.getId());
				updateList.add(current);
				currentData.remove(key);
			} else {
				// if originalItem not exist in map, originalItem need to delete
				deleteList.add(originalItem);
			}
		}

		if (!currentData.isEmpty()) {
			// if map still has data, these data not exist in database, we should insert these data
			for (Entry<String, T> entry : currentData.entrySet()) {
				addList.add(entry.getValue());
			}
		}
		
		int i = 0;
		while (i < deleteList.size() && i < addList.size()) {
			T item = addList.get(i);
			item.setId(deleteList.get(i).getId());
			updateList.add(item);
			i++;
		}
		
		addList = addList.subList(i, addList.size());
		deleteList = deleteList.subList(i, deleteList.size());

		batchDao.batchDataOperation(updateList, dataBuilder.renderUpdateIbatis());

		batchDao.batchDataOperation(addList, dataBuilder.renderAddIbatis());

		batchDao.batchDataOperation(deleteList, dataBuilder.renderDeleteIbatis());
	}

    /**
     * @see cn.vobile.trackerspt.service.homereport.HomeReportService#dealData(java.util.List, java.util.List, cn.vobile.trackerspt.service.homereport.HomeReportDataBuilder)
     */
    public <T extends BaseEntity> void dealData(List<T> currentData, List<T> originalData, HomeReportDataBuilder<T> dataBuilder) {
        Map<String, T> map = new HashMap<String, T>();
        for (T data : currentData) {
            map.put(dataBuilder.renderKey(data), data);
        }

        dealData(map, originalData, dataBuilder);
    }

}

         * 考虑到每个实体的key值会由不同的数据表字段组成，并且每个调用的方法对应的数据表也是不同的，因此在实现两个List对比处理的时候，都要继承抽象类

<span style="color:#FF0000;"><strong>HomeReportDataBuilder<T>并且重写里面的4个方法。</strong></span>