Java中的NavigableMap higherKey（）方法

NavigableMap接口的 higherKey（） 方法用于返回严格大于给定键的最小键，如果没有这样的键，则返回null。

语法:

public K higherKey(K key)

参数: 此方法将 键k 作为参数。

返回值: 此方法返回 大于键的最小键 ，如果没有这样的键，则返回 null 。

异常: 如果指定的键为null并且该映射使用自然排序，或者其比较器不允许null键，则此方法会抛出 NullPointerException 。

以下是说明 higherKey（） 方法的示例：

示例1:

// Java program to demonstrate
// higherKey() method
// for <Integer, String>
import java.util.*;
public class GFG1 {
 public static void main(String[] args) throws Exception {
   try {
     // Creating object of NavigableMap
     NavigableMap <Integer, String> navmap = new TreeMap <Integer, String> ();

     // Populating the map
     navmap.put(1, "One");
     navmap.put(2, "Two");
     navmap.put(3, "Three");
     navmap.put(4, "Four");
     navmap.put(5, "Five");

     // Printing the TreeMap
     System.out.println("NavigableMap: " + navmap);

     // Getting higher key value for 3
     // using higherKey() method
     int value = navmap.higherKey(3);

     // Printing the value
     System.out.println("The higherKey value " + " for 3: " + value);
   } catch(NullPointerException e) {
     System.out.println("Exception thrown : " + e);
   }
 }
}

输出:

NavigableMap: {1=One, 2=Two, 3=Three, 4=Four, 5=Five}
The higherKey value  for 3: 4

示例2: NullPointerException

// Java program to demonstrate
// higherKey() method
// for NullPointerException
import java.util.*;
public class GFG1 {
 public static void main(String[] args) throws Exception {
   try {
     // Creating object of TreeMap <Integer, String>
     NavigableMap <Integer, String> navmap = new TreeMap <Integer, String> ();

     // Populating the TreeMap
     navmap.put(1, "One");
     navmap.put(2, "Two");
     navmap.put(3, "Three");
     navmap.put(4, "Four");
     navmap.put(5, "Five");

     // Printing the NavigableMap
     System.out.println("TreeMap: " + navmap);

     // Getting higher key value for null
     // Using higherKey() method
     System.out.println("Trying to get higherKey" + " value for null");

     int value = navmap.higherKey(null);

     // Printing the value
     System.out.println("Value is: " + value);
   } catch(NullPointerException e) {
     System.out.println("Exception thrown : " + e);
   }
 }
}

输出:

TreeMap: {1=One, 2=Two, 3=Three, 4=Four, 5=Five}
Trying to get higherKey value for null
Exception thrown : java.lang.NullPointerException