Java 中的 TreeMap higherKey()方法，带示例

原文:https://www . geesforgeks . org/tree map-higher key-method-in-Java-with-examples/

Java . util . treemap类的HierKey()方法用于返回严格大于给定密钥的最小密钥，如果没有这样的密钥，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:该方法返回最小键大于键，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。 以下是举例说明 higherKey() 方法 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[] argv) throws Exception
    {
        try {

            // creating object of TreeMap<Integer, String>
            TreeMap<Integer, String>
                treemap = new TreeMap<Integer, String>();

            // populating tree map
            treemap.put(1, "One");
            treemap.put(2, "Two");
            treemap.put(3, "Three");
            treemap.put(4, "Four");
            treemap.put(5, "Five");

            // printing the TreeMap
            System.out.println("TreeMap: " + treemap);

            // getting higher key value for 3
            // using higherKey() method
            int value = treemap.higherKey(3);

            // printing the value
            System.out.println("The higherKey value "
                               + " for 3: " + value);
        }

        catch (NullPointerException e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}

Output: 

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

例 2: 为零点异常T4】

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[] argv) throws Exception
    {
        try {

            // creating object of TreeMap<Integer, String>
            TreeMap<Integer, String>
                treemap = new TreeMap<Integer, String>();

            // populating tree map
            treemap.put(1, "One");
            treemap.put(2, "Two");
            treemap.put(3, "Three");
            treemap.put(4, "Four");
            treemap.put(5, "Five");

            // printing the TreeMap
            System.out.println("TreeMap: " + treemap);

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

            int value = treemap.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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