Java中的 ConcurrentSkipListMap containsKey() 方法及示例

Java .util.concurrent.ConcurrentSkipListMap的containsKey()方法是Java中的一个内置函数，如果此映射中存在指定元素，则返回 true 布尔值，否则返回 false。

句法：

public boolean containsKey(Object ob)

参数：该函数接受一个强制参数ob ，该参数指定要测试其在此映射中的存在的键。

返回值：如果此映射包含指定键的映射，则该函数返回 true。

下面的程序说明了上述方法：

方案一：

// Java Program Demonstrate containsKey()
// method of ConcurrentSkipListMap
  
import java.util.concurrent.*;
  
class GFG {
    public static void main(String[] args)
    {
  
        // Initializing the map
        ConcurrentSkipListMap
            mpp = new ConcurrentSkipListMap();
  
        // Adding elements to this map
        for (int i = 1; i <= 5; i++)
            mpp.put(i, i);
  
        // Checks if 9 is present in the map
        if (mpp.containsKey(9))
            System.out.println("9 is present"
                               + " in the mpp.");
        else
            System.out.println("9 is not present"
                               + " in the mpp.");
    }
}

方案二：

// Java Program Demonstrate containsKey()
// method of ConcurrentSkipListMap
  
import java.util.concurrent.*;
  
class GFG {
    public static void main(String[] args)
    {
  
        // Initializing the map
        ConcurrentSkipListMap
            mpp = new ConcurrentSkipListMap();
  
        // Adding elements to this map
        for (int i = 1; i <= 5; i++)
            mpp.put(i, i);
  
        // Checks if 4 is present in the map
        if (mpp.containsKey(4))
            System.out.println("4 is present"
                               + " in the mpp.");
        else
            System.out.println("4 is not present"
                               + " in the mpp.");
    }
}

参考： https://docs.oracle.com/javase/9/docs/api/ Java/util/concurrent/ConcurrentSkipListMap.html#containsKey-java.lang.Object-