In this shot, we will learn how to use the TreeMap.firstKey()
method in Java.
The TreeMap.firstKey()
method is present in the TreeMap
class inside the java.util
package. The TreeMap.firstKey()
is used to obtain the least key currently present in the map.
The syntax of the TreeMap.firstKey()
method is given below:
public K firstKey()
The TreeMap.firstKey()
does not accept any parameters.
The TreeMap.firstKey()
method returns one value:
Let’s have a look at the code.
import java.util.*;class Main{public static void main(String[] args){TreeMap<Integer, String> t1 = new TreeMap<Integer, String>();t1.put(1, "Let's");t1.put(5, "see");t1.put(2, "TreeMap class");t1.put(27, "methods");t1.put(9, "in java.");System.out.println("The least key in the map is: " + t1.firstKey());TreeMap<String, Integer> t2 = new TreeMap<String, Integer>();t2.put("ab", 5);t2.put("baa", 1);t2.put("cbc", 2);t2.put("d", 27);t2.put("e", 9);System.out.println("The least key in the map is: " + t2.firstKey());}}
Line 1: We import the required package.
Line 2: We make a Main
class.
Line 4: We make a main()
function.
Line 6: We declare a TreeMap
consisting of keys of type Integer
and values of type String
.
Lines 8 to 12: We insert values in the TreeMap
by using the TreeMap.put()
method.
Line 14: We use TreeMap.firstKey()
method and displayed the lowest key present in the TreeMap
with a message.
Lines 17 to 26: We create another TreeMap
object which contains keys of type String
and the values of type Integer
. Then, we can see in the output that the lowest key would be considered based on the alphabetic order in the case of strings.
So, this is the way to use the TreeMap.firstKey()
method in Java.