Java中的 NavigableMap ceilingKey() 方法

Java中NavigableMap接口的ceilingKey()方法用于返回大于或等于给定键的最小键，如果不存在该键则返回null。

语法：

K ceilingKey(K key)

其中，K 是该地图容器维护的 Key 的类型。

参数：它接受单个参数Key ，该参数是要映射的键，并且是此集合接受的键类型。

返回值：它返回大于或等于给定键的最小键，如果不存在这样的键，则返回 null。

下面的程序说明了Java中的 ceilingKey() 方法：

程序1 ：当key为整数时。

// Java code to demonstrate the working of
// ceilingKey()  method
  
import java.io.*;
import java.util.*;
  
public class GFG {
  
    public static void main(String[] args)
    {
  
        // Declaring the NavigableMap of Integer and String
        NavigableMap tmmp = new TreeMap<>();
  
        // assigning the values in the NavigableMap
        // using put()
        tmmp.put(2, "two");
        tmmp.put(7, "seven");
        tmmp.put(3, "three");
  
        // Use of ceilingKey()
        // returns 7( next greater key)
        System.out.println("The next greater key of 6 is : "
                           + tmmp.ceilingKey(6));
  
        // returns "null" as no value present
        // greater than or equal to number
        System.out.println("The next greater key of 3 is : " 
                                       + tmmp.ceilingKey(3));
    }
}

输出：

The next greater key of 6 is : 7
The next greater key of 3 is : 3

方案二：当key为字符串时。

// Java code to demonstrate the working of
// ceilingKey()  method
  
import java.io.*;
import java.util.*;
  
public class GFG {
  
    public static void main(String[] args)
    {
  
        // Declaring the NavigableMap of Integer and String
        NavigableMap tmmp = new TreeMap<>();
  
        // assigning the values in the NavigableMap
        // using put()
        tmmp.put("one", "two");
        tmmp.put("six", "seven");
        tmmp.put("two", "three");
  
        // Use of ceilingKey()
        // returns 7( next greater key)
        System.out.println("The next greater key of five is : "
                           + tmmp.ceilingKey("five"));
  
        // returns "null" as no value present
        // greater than or equal to number
        System.out.println("The next greater key of six is : " + 
                                         tmmp.ceilingKey("six"));
    }
}

输出：

The next greater key of five is : one
The next greater key of six is : six

参考：https: Java/util/NavigableMap.html#ceilingKey(K)