Java TreeMap higherKey() Method

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Description

TheJava TreeMap higherKey(K key) method is used to return the least key strictly greater than the given key, or null if there is no such key.

Declaration

Following is the declaration for java.util.TreeMap.higherKey() method.

public K higherKey(K key)

Parameters

key − This is the key to be matched.

Return Value

The method call returns the least key greater than key, or null if there is no such key.

Exception

• ClassCastException − This exception is thrown if the specified key cannot be compared with the keys currently in the map.

• NullPointerException − This exception is thrown if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys.

Getting Higher Key based on given Key from a TreeMap of Integer, Integer Pairs Example

The following example shows the usage of Java TreeMap higherKey() method to get least key strictly greater than the given key in the map. We've created a TreeMap object of Integer,Integer pairs. Then few entries are added, and using higherKey() we're printing relevant key to the given key.

package com.tutorialspoint;

import java.util.TreeMap;

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

      // creating tree map 
      TreeMap<Integer, Integer> treemap = new TreeMap<>();

      // populating tree map
      treemap.put(2, 2);
      treemap.put(1, 1);
      treemap.put(3, 3);
      treemap.put(6, 6);
      treemap.put(5, 5);

      // getting higher key for key 4          
      System.out.println("Checking values of the map");
      System.out.println("Value is: "+ treemap.higherKey(3));
   }     
}

Output

Let us compile and run the above program, this will produce the following result.

Checking values of the map
Value is: 5

Getting Higher Entry based on given Key from a TreeMap of Integer, String Pairs Example

The following example shows the usage of Java TreeMap higherKey() method to get least key strictly greater than the given key in the map. We've created a TreeMap object of Integer,String pairs. Then few entries are added, and using higherKey() we're printing relevant key to the given key.

package com.tutorialspoint;

import java.util.TreeMap;

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

      // creating tree map 
      TreeMap<Integer, String> treemap = new TreeMap<>();

      // populating tree map
      treemap.put(2, "two");
      treemap.put(1, "one");
      treemap.put(3, "three");
      treemap.put(6, "six");
      treemap.put(5, "five");

      // getting higher key for key 4          
      System.out.println("Checking values of the map");
      System.out.println("Value is: "+ treemap.higherKey(3));
   }     
}

Output

Let us compile and run the above program, this will produce the following result.

Checking values of the map
Value is: 5

Getting Higher Entry based on given Key from a TreeMap of Integer, Object Pairs Example

The following example shows the usage of Java TreeMap higherKey() method to get least key strictly greater than the given key in the map. We've created a TreeMap object of Integer,Student pairs. Then few entries are added, and using higherKey() we're printing relevant key to the given key.

package com.tutorialspoint;

import java.util.TreeMap;

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

      // creating tree map 
      TreeMap<Integer, Student> treemap = new TreeMap<>();

      // populating tree map
      treemap.put(2, new Student(2, "Robert"));
      treemap.put(1, new Student(1, "Julie"));  
      treemap.put(3, new Student(3, "Adam"));
      treemap.put(6, new Student(6, "Julia"));
      treemap.put(5, new Student(5, "Tom"));

      // getting higher key for key 4          
      System.out.println("Checking values of the map");
      System.out.println("Value is: "+ treemap.higherKey(3));
   }     
}
class Student {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
   @Override
   public boolean equals(Object obj) {
      if(obj == null) return false;
      Student s = (Student)obj;
      return this.rollNo == s.rollNo && this.name.equalsIgnoreCase(s.name);
   }
}

Output

Let us compile and run the above program, this will produce the following result.

Checking values of the map
Value is: 5