Java 中的 ConcurrentSkipListMap ceiling key()方法，带示例

原文:https://www . geeksforgeeks . org/concurrentskiplistmap-ceiling key-method-in-Java-with-examples/

java . util . concurrentskiplistmap的 ceilingKey() 方法是 Java 中的一个内置函数，它返回大于或等于给定键的最小键。如果没有这样的值，则返回 null。当没有键时，该方法引发 NullPointerException。

语法:

public K ceilingKey(K key)

参数:该功能接受单个强制参数键，指定该键。

返回值:该函数返回大于或等于键的最小键，如果没有这样的键，则返回空。

异常:该方法抛出两种类型的异常:

  • ClassCastException: 如果指定的关键点无法与当前地图中的关键点进行比较，并且
  • NullPointRexception:如果指定的键为空。

下面的程序说明了上面的方法: 程序 1:

// Java program to demonstrate
// ceilingkey method in java

import java.util.concurrent.ConcurrentSkipListMap;

class GFG {
    public static void main(String[] args)
    {

        // Initializing the set
        // using ConcurrentSkipListMap()
        ConcurrentSkipListMap<Integer, Integer>
            mpp = new ConcurrentSkipListMap<Integer,
                                            Integer>();

        // Adding elements to this set
        mpp.put(1, 1);
        mpp.put(5, 2);
        mpp.put(2, 7);

        // Printing the ConcurrentSkipListMap
        // Always in ascending order

        System.out.println("Map: "
                           + mpp);

        System.out.println("key greater than or equal 3: "
                           + mpp.ceilingKey(3));

        System.out.println("key greater than or equal 2: "
                           + mpp.ceilingKey(2));
    }
}

Output:

Map: {1=1, 2=7, 5=2}
key greater than or equal 3: 5
key greater than or equal 2: 2

程序 2:

// Java program to demonstrate
// ceilingkey method in java
import java.util.concurrent.ConcurrentSkipListMap;

class GFG {
    public static void main(String[] args)
    {

        // Initializing the set
        // using ConcurrentSkipListMap()
        ConcurrentSkipListMap<Integer, Integer>
            mpp = new ConcurrentSkipListMap<Integer,
                                            Integer>();

        // Adding elements to this set
        mpp.put(11, 1);
        mpp.put(51, 42);
        mpp.put(92, 7);

        // Printing the ConcurrentSkipListMap
        // Always in ascending order

        System.out.println("Map: "
                           + mpp);

        System.out.println("key greater than or equal 11: "
                           + mpp.ceilingKey(11));

        System.out.println("key greater than or equal 51: "
                           + mpp.ceilingKey(51));
    }
}

Output:

Map: {11=1, 51=42, 92=7}
key greater than or equal 11: 11
key greater than or equal 51: 51

参考:https://docs . Oracle . com/javase/8/docs/API/Java/util/concurrentskiplistmap . html # ceilingKey-K-

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