Java中的 ConcurrentSkipListMap clear() 方法及示例

Java .util.concurrent.ConcurrentSkipListMap的clear()方法是Java中的一个内置函数，它从该映射中删除所有映射。这意味着地图中的所有元素都将被删除并返回一个空地图。

句法：

public void clear()

参数：该函数不接受任何参数。

返回值：该函数从该映射中删除所有映射。

下面的程序说明了上述方法：

方案一：

// Java Program Demonstrate clear()
// method of ConcurrentSkipListMap
  
import java.util.concurrent.*;
  
class GFG {
    public static void main(String[] args)
    {
  
        // Initializing the map
        ConcurrentSkipListMap
            mpp = new ConcurrentSkipListMap();
  
        // adding elements in map
        for (int i = 1; i <= 5; i++)
            mpp.put(i, i);
  
        // print original map
        System.out.println("map elements are: "
                           + mpp);
  
        mpp.clear();
  
        // after clear() operation
        System.out.println("after clear the map is: "
                           + mpp);
    }
}

输出：

map elements are: {1=1, 2=2, 3=3, 4=4, 5=5}
after clear the map is: {}

方案二：

// Java Program Demonstrate clear()
// method of ConcurrentSkipListMap
  
import java.util.concurrent.*;
  
class GFG {
    public static void main(String[] args)
    {
  
        // Initializing the map
        ConcurrentSkipListMap
            mpp = new ConcurrentSkipListMap();
  
        // adding elements in map
        for (int i = 1; i <= 10; i++)
            mpp.put(i, i);
  
        // print original map
        System.out.println("map elements are: "
                           + mpp);
  
        mpp.clear();
  
        // after clear() operation
        System.out.println("after clear the map is: "
                           + mpp);
    }
}

输出：

map elements are: {1=1, 2=2, 3=3, 4=4, 5=5, 6=6, 7=7, 8=8, 9=9, 10=10}
after clear the map is: {}

参考： https: Java/util/concurrent/ConcurrentSkipListMap.html#clear–