导入包
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
1.循环打印键和值
System.out.println("*****循环map集合,并打印键和值****");
Map<Long, Object> map= new HashMap<Long, Object>();
map.put(1L, 1);
map.put(2L, "二");
map.put(3L, new ArrayList<String>());
for(Long key : map.keySet()){
System.out.println("key:"+key +" "+"value:"+map.get(key));
}
打印结果
*****循环map集合,并打印键和值****
key:1 value:1
key:2 value:二
key:3 value:[]
2.获取键的集合并转化成List(循环打印)
System.out.println("*****获取map键并转化成list集合****");
List<Long> keyList= new ArrayList<Long>(map.keySet());
for(Long key : keyList) {
System.out.println("key:"+key);
}
打印结果
*****获取map键并转化成list集合****
key:1
key:2
key:3
3.循环获取mapkey和value的类型
System.out.println("*****循环获取mapkey和value的类型****");
Set keys = map.keySet();
Iterator it = keys.iterator();
while (it.hasNext()){
Object key = it.next();
Object value = map.get(key);
System.out.println("key类型:"+key.getClass().getName());
System.out.println("值类型:"+value.getClass().getName());
}
打印结果
*****循环获取mapkey和value的类型****
key类型:java.lang.Long
值类型:java.lang.Integer
key类型:java.lang.Long
值类型:java.lang.String
key类型:java.lang.Long
值类型:java.util.ArrayList