Java Map. Containskey() method: judge whether the map collection object contains the specified key name
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Java
containsKey(Object key)
Typical application
public static void main(String[] args){ Map map = new HashMap(); //定义Map对象 map.put("apple","新鲜的苹果"); //向集合中添加对象 map.put("computer","配置优良的计算机"); map.put("book","堆积成山的图书"); map.put("time",new Date()); String key = "book"; boolean contains=map.containsKey(key); //判断是否包含指定的键值 if(contains){ //如果条件为真 System.out.println("在Map集合中包含键名"+key); //输出信息 }else{ System.out.println("在Map集合中不包含键名"+key); } }
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