weakhashmap

WeakHashMap类的keySet()方法 (WeakHashMap Class keySet() method)

• keySet() method is available in java.util package.

  keySet()方法在java.util包中可用。

• keySet() method is used to retrieve all the key exists in this map to be viewed in a set.

  keySet()方法用于检索此映射中存在的所有键，以在集合中进行查看。

• keySet() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.

  keySet()方法是一种非静态方法，只能通过类对象访问，如果尝试使用类名访问该方法，则会收到错误消息。

• keySet() method does not throw an exception at the time of viewing elements in a set.

  在查看集合中的元素时， keySet()方法不会引发异常。

Syntax:

句法：

    public Set keySet();

Parameter(s):

参数：

• It does not accept any parameter.

  它不接受任何参数。

Return value:

返回值：

The return type of the method is Set, it returns existing keys in this map to be viewed in a set.

该方法的返回类型为Set ，它返回此映射中的现有键以在集合中查看。

Example:

例：

// Java program to demonstrate the example
// of Set keySet() method of WeakHashMap
import java.util.*;
public class KeySetOfWeakHashMap {public static void main(String[] args) {// Instantiates a WeakHashMap object
Map < Integer, String > map = new WeakHashMap < Integer, String > ();
// By using put() method is to add
// key-value pairs in a WeakHashMap
map.put(10, "C");
map.put(20, "C++");
map.put(50, "JAVA");
map.put(40, "PHP");
map.put(30, "SFDC");
// Display WeakHashMap
System.out.println("WeakHashMap: " + map);
// By using keySet() method is to
// return the set of of keys exists
// in this WeakHashMap to be viewed in a Set
Set s = map.keySet();
// Display status
System.out.print("map.keySet(): ");
System.out.println(s);
}
}

Output

输出量

WeakHashMap: {30=SFDC, 40=PHP, 10=C, 20=C++, 50=JAVA}
map.keySet(): [30, 40, 10, 20, 50]

翻译自: https://www.includehelp.com/java/weakhashmap-keyset-method-with-example.aspx

weakhashmap