List<T> Map :List里面的数据类型包含Map;
Map List<T>:Map里面value的数据类型包含List;
测试案例:
java
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
public class day20 {
public static void main(String[] args) {
Map<String,Object> map1 = new HashMap<>();
map1.put("name","小婷");
map1.put("age",20);
Map<String,Object> map2 = new HashMap<>();
map2.put("name","小霞");
map2.put("age",22);
Map<String,Object> map3 = new HashMap<>();
map3.put("name","小桐");
map3.put("age",24);
// Map集合:List<Map<String,Object>>:
List<Map<String,Object>> list = new ArrayList<>();
list.add(map1);
list.add(map2);
list.add(map3);
for(Map<String,Object> map :list) {
System.out.println("List<T> Map:"+map);
}
System.out.println("---------------------");
// 集合Map:Map<String,Object>:
Map<String,Object> map = new HashMap<>();
List<Map<String,Object>> list2 = new ArrayList<>();
Map<String,Object> map4 = new HashMap<>();
map4.put("name","小英");
map4.put("age",20);
Map<String,Object> map5 = new HashMap<>();
map5.put("name","小红");
map5.put("age",22);
Map<String,Object> map6 = new HashMap<>();
map6.put("name","小婵");
map6.put("age",24);
list2.add(map4);
list2.add(map5);
list2.add(map6);
map.put("list1", list);
map.put("list2", list2);
System.out.println("Map List<T>1:"+map);
System.out.println("---------------------");
Iterator<Map.Entry<String, Object>> it = map.entrySet().iterator();
while(it.hasNext()){
Map.Entry<String, Object> entry = it.next();
System.out.println("Map List<T>2:"+"key="+entry.getKey()+" value="+entry.getValue());
}
}
}
测试输出:
java
List<T> Map:{name=小婷, age=20}
List<T> Map:{name=小霞, age=22}
List<T> Map:{name=小桐, age=24}
---------------------
Map List<T>1:{list1=[{name=小婷, age=20}, {name=小霞, age=22}, {name=小桐, age=24}], list2=[{name=小英, age=20}, {name=小红, age=22}, {name=小婵, age=24}]}
---------------------
Map List<T>2:key=list1 value=[{name=小婷, age=20}, {name=小霞, age=22}, {name=小桐, age=24}]
Map List<T>2:key=list2 value=[{name=小英, age=20}, {name=小红, age=22}, {name=小婵, age=24}]