Java TreeMap navigableKeySet() Method

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Description

The Java TreeMap navigableKeySet() method is used to return a NavigableSet view of the keys contained in this map. The set's iterator returns the keys in ascending order. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa.

Declaration

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

public NavigableSet<K> navigableKeySet()

Parameters

NA

Return Value

The method call returns a navigable set view of the keys in this map.

Exception

NA

Getting Navigable Set View from a TreeMap of Integer,Integer Pair Example

The following example shows the usage of Java TreeMap navigableKeySet() method to get a NavigableSet view of the keys of this map. We've created a TreeMap object of Integer,Integer pairs. Then few entries are added, and using navigableKeySet() we're printing a Navigable Set of keys of the map.

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 navigable key set 
      System.out.println("Checking key set value");
      System.out.println("Value is: "+ treemap.navigableKeySet());
   }    
}

Output

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

Checking key set value
Value is: [1, 2, 3, 5, 6]

Getting Navigable Set View from a TreeMap of Integer,String Pair Example

The following example shows the usage of Java TreeMap navigableKeySet() method to get a NavigableSet view of the keys of this map. We've created a TreeMap object of Integer,String pairs. Then few entries are added, and using navigableKeySet() we're printing a Navigable Set of keys of the map.

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 navigable key set 
      System.out.println("Checking key set value");
      System.out.println("Value is: "+ treemap.navigableKeySet());
   }    
}

Output

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

Checking key set value
Value is: [1, 2, 3, 5, 6]

Getting Navigable Set View from a TreeMap of Integer,Object Pair Example

The following example shows the usage of Java TreeMap navigableKeySet() method to get a NavigableSet view of the keys of this map. We've created a TreeMap object of Integer,Student pairs. Then few entries are added, and using navigableKeySet() we're printing a Navigable Set of keys of the map.

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 navigable key set 
      System.out.println("Checking key set value");
      System.out.println("Value is: "+ treemap.navigableKeySet());
   }    
}
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 key set value
Value is: [1, 2, 3, 5, 6]