hashMap或者concurrenthashmap 调用entrySet方法都出现导致内存泄漏情况：java.lang.OutOfMemoryError: Java heap space经过核实map.entrySet().size() map.keySet().size() map.values...

Java Map的containsKey(Object key)和containsValue(Object value)方法

public void testContainsKeyOrValue(){ Scanner sc = new Scanner(System.in); //Key System.out.println("请输入要查询的学生id："); String id = sc.next(); System.out...

《Java核心技术卷Ⅱ　高级特性（原书第10版）》一1.3　filter、map和flatMap方法

1.3　filter、map和flatMap方法流的转换会产生一个新的流，它的元素派生自另一个流中的元素。我们已经看到了f?ilter转换会产生一个流，它的元素与某种条件相匹配。下面，我们将一个字符串流转换为了只包含长单词的另一个流： f?ilter的引元是Predicate，即从T到boolea...

java中集合类中Collection接口中的Map接口的常用方法熟悉

1:Map接口提供了将键映射到值的对象。一个映射不能包含重复的键；每个键最多只能映射到一个值。Map接口中同样提供了集合的常用方法。 2：由于Map集合中的元素是通过key,value，进行存储的，要获取集合中指定的key或者value值，需要先通过相应的方法获取key集合或者value集合，再遍历...

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