map

最高效的遍历map的每个entry的方法
for (Map.Entry entry : map.entrySet()){ 
    int key = (int) entry.getKey(); 
    int value = (int) entry.getValue();
}
初始化一个不可变Map
public class Test{ private static Map
 
   map1 = new HashMap<>(); 
static { 
    map1.put(8,9); 
    map1.put(88,99); 
    map1 = Collections.unmodifiableMap(map1); 
    }
}