import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
public class MapDemo {
public static void main(String[] args) {
Map map = new HashMap<>();
map.put("1", "Value1");
map.put("2", "Value2");
map.put("3", "Value3");
map.put(null, "11");
//第一ç§ï¼šæ™®é使用，二次å–值
System.out.println("通过Map.keySeté历keyå’Œvalue：");
for (String key :
map.keySet()) {
System.out.println(key);
}
for (String value :
map.values()) {
System.out.println(value);
}
//第二ç§
System.out.println("通过Map.entrySet使用iteratoré历keyå’Œvalue：");
Iterator> iterator = map.entrySet().iterator();
while (iterator.hasNext()) {
Map.Entry entry = iterator.next();
System.out.println("key=" + entry.getKey() + " and value=" + entry.getValue());
}
//第三ç§ï¼šæŽ¨è，尤其是容é‡å¤§æ—¶
System.out.println("通过Map.entrySeté历keyå’Œvalue");
for (Map.Entry entry : map.entrySet()
) {
System.out.println("key=" + entry.getKey() + " and value=" + entry.getValue());
}
//第四ç§ï¼šå°¤å…¶æŽ¨è
map.forEach((k, v) -> System.out.println("Key=" + k + ",Value=" + v));
Vector vector = new Vector();
vector.add("11");
// Map stringIntegerMap=new ConcurrentHashMap<>();
// stringIntegerMap.put(null,11);
HashSet hashSet = new HashSet();
hashSet.add(11);
}
}