java List To Map 及 List To MapMap, List To MapList 通用工具方法

平常在工作中經常用到, List 向Map轉換,

或者轉換成 Map<Key, Map<Key2, Val >>,

也有轉換成 Map<K, List<V>>,

方便分組提取數據, 雖然在jdk 1.8後有其它方法, 但是還是覺得工具類用起來方便, 下面就是代碼實現:

package test;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.util.CollectionUtils;

/** 
 * 將List轉換爲 Map的工具類
 * @author guishuanglin 2020-04-20
 */
public class TestListToMap {
	private static final Log logger = LogFactory.getLog(TestListToMap.class);
	
	/**
	 * 將List轉換爲 Map<K, Map<K2, V>>
	 * @param dataList 需要轉換的數據
	 * @param methodNameK  取K 值的方法名
	 * @param methodNameK2   取K2 值的方法名
	 * @return
	 */
	@SuppressWarnings({ "unchecked" })
	public static <K,K2,V> Map<K, Map<K2, V>> ListToMapMap(List<V> dataList, String methodNameK, String methodNameK2) {
		if (CollectionUtils.isEmpty(dataList)) {
			return null;
		}
		if (methodNameK == null || "".equals(methodNameK)) {
			logger.error("param methodNameK is null");
			return null;
		}
		if (methodNameK2 == null || "".equals(methodNameK2)) {
			logger.error("param methodNameK2 is null");
			return null;
		}
		Method m = null;
		Method m2 = null;
		V dataObj = dataList.get(0);
		try {
			m = dataObj.getClass().getDeclaredMethod(methodNameK);
			m2 = dataObj.getClass().getDeclaredMethod(methodNameK2);
		} catch (NoSuchMethodException e) {
			logger.error("ListToMapMap error", e);
		}
		Map<K, Map<K2,V>> dataMap = new HashMap<K, Map<K2,V>>();
		for (V data : dataList) {
			if(data != null){
				try {
					K k = (K)m.invoke(data, new Object[]{});
					K2 k2 = (K2)m2.invoke(data, new Object[]{});
					Map<K2,V> temp = null;
					if (dataMap.containsKey(k)) {
						temp = dataMap.get(k);
					} else {
						temp = new HashMap<K2,V>();
						dataMap.put(k, temp);
					}
					temp.put(k2, data);
				} catch (SecurityException e) {
					e.printStackTrace();
				} catch (IllegalArgumentException e) {
					e.printStackTrace();
				} catch (IllegalAccessException e) {
					e.printStackTrace();
				} catch (InvocationTargetException e) {
					e.printStackTrace();
				}					
			}
		}
		return dataMap;
	}
	
	/**
	 * 將List轉換爲 Map<K, List<V>>
	 * @param dataList 需要轉換的數據
	 * @param methodNameK  取K 值的方法名
	 * @return
	 */
	@SuppressWarnings({ "unchecked" })
	public static <K, V> Map<K, List<V>> ListToMapList(List<V> dataList, String methodNameK) {
		if (CollectionUtils.isEmpty(dataList)) {
			return null;
		}
		if (methodNameK == null || "".equals(methodNameK)) {
			logger.error("param methodNameK is null");
			return null;
		}
		Method method = null;
		V dataObj = dataList.get(0);
		try {
			method = dataObj.getClass().getDeclaredMethod(methodNameK);
		} catch (NoSuchMethodException e) {
			logger.error("ListToMapList error", e);
		}
		Map<K, List<V>> dataMap = new HashMap<K, List<V>>();
		for (V data : dataList) {
			if(data != null){
				try {
					K k = (K)method.invoke(data, new Object[]{});
					List<V> temp = null;
					if (dataMap.containsKey(k)) {
						temp = dataMap.get(k);
					} else {
						temp = new ArrayList<V>();
						dataMap.put(k, temp);
					}
					temp.add(data);
				} catch (SecurityException e) {
					e.printStackTrace();
				} catch (IllegalArgumentException e) {
					e.printStackTrace();
				} catch (IllegalAccessException e) {
					e.printStackTrace();
				} catch (InvocationTargetException e) {
					e.printStackTrace();
				}					
			}
		}
		return dataMap;
	}
	
	/**
	 * 將List轉換爲map
	 * @param dataList 需要轉換的數據
	 * @param methodNameK  取K 值的方法名
	 * @return
	 */
	@SuppressWarnings({ "unchecked" })
	public static <K, V> Map<K, V> ListToMap(List<V> dataList, String methodNameK) {
		if (CollectionUtils.isEmpty(dataList)) {
			return null;
		}
		if (methodNameK == null || "".equals(methodNameK)) {
			logger.error("param methodNameKK is null");
			return null;
		}
		Method method = null;
		V dataObj = dataList.get(0);
		try {
			method = dataObj.getClass().getDeclaredMethod(methodNameK);
		} catch (NoSuchMethodException e) {
			logger.error("ListToMapList error", e);
		}
		Map<K, V> dataMap = new HashMap<K, V>();
		for (V data : dataList) {
			if(data != null){
				try {
					K k = (K)method.invoke(data, new Object[]{});
					dataMap.put(k, data);
				} catch (SecurityException e) {
					e.printStackTrace();
				} catch (IllegalArgumentException e) {
					e.printStackTrace();
				} catch (IllegalAccessException e) {
					e.printStackTrace();
				} catch (InvocationTargetException e) {
					e.printStackTrace();
				}					
			}
		}
		return dataMap;
	}
		
	 public static void main(String[] args) {
		//自己可以寫測試代碼
	 }
}

測試代碼就不上了, 上面的類是完整的, 如果沒有 springframework 包, 可以自己用代碼判斷是不是空List,

logging 包也不是必須的, 如果沒有可以用java自己的輸出.