Java 中的 NavigableMap higherKey()方法

原文:https://www . geeksforgeeks . org/naviglambap-higher key-method-in-Java/

导航映射接口的 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:该方法以键 k 为参数。

返回值:该方法返回大于键的最小键，或空值如果没有这样的键。

异常:如果指定的键为空，并且该映射使用自然排序，或者其比较器不允许空键，则该方法抛出空指针异常。

以下是说明 higherKey() 方法的示例:

例 1:

Java 语言(一种计算机语言，尤用于创建网站)

// 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);
        }
    }
}

Output: 

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

示例 2: 适用于空指针异常

Java 语言(一种计算机语言，尤用于创建网站)

// 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 tree map
            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);
        }
    }
}

Output: 

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

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