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Java Program to Sort map by keys
In this article, we will understand how to sort map by keys. The Java Map interface, java.util.Map, represents a mapping between a key and a value. More specifically, a Java Map can store pairs of keys and values. Each key is linked to a specific value.
Below is a demonstration of the same −
Suppose our input is −
Input map: {1=Scala, 2=Python, 3=Java}The desired output would be −
The sorted map with the key:
{1=Scala, 2=Python, 3=Java}Algorithm
Step 1 - START Step 2 - Declare namely Step 3 - Define the values. Step 4 - Create a Map structure, and add values to it using the ‘put’ method. Step 5 - Create a TreeMap of strings. Step 6 - The Map sorts the values based on keys and stores it in TreeMap. Step 7 - Display this on the console. Step 8 - Stop
Example 1
Here, we bind all the operations together under the ‘main’ function.
import java.util.HashMap;
import java.util.Map;
import java.util.TreeMap;
public class Demo {
public static void main(String[] args) {
System.out.println("The required packages have been imported");
Map<String, String> input_map = new HashMap<>();
input_map.put("1", "Scala");
input_map.put("3", "Java");
input_map.put("2", "Python");
System.out.println("The map is defined as: " + input_map);
TreeMap<String, String> result_map = new TreeMap<>(input_map);
System.out.println("\nThe sorted map with the key: \n" + result_map);
}
}Output
The required packages have been imported
The map is defined as: {1=Scala, 2=Python, 3=Java}
The sorted map with the key:
{1=Scala, 2=Python, 3=Java}Example 2
Here, we encapsulate the operations into functions exhibiting object oriented programming.
import java.util.HashMap;
import java.util.Map;
import java.util.TreeMap;
public class Demo {
static void sort( Map<String, String> input_map){
TreeMap<String, String> result_map = new TreeMap<>(input_map);
System.out.println("\nThe sorted map with the key: \n" + result_map);
}
public static void main(String[] args) {
System.out.println("The required packages have been imported");
Map<String, String> input_map = new HashMap<>();
input_map.put("1", "Scala");
input_map.put("3", "Java");
input_map.put("2", "Python");
System.out.println("The map is defined as: " + input_map);
sort(input_map);
}
}Output
The required packages have been imported
The map is defined as: {1=Scala, 2=Python, 3=Java}
The sorted map with the key:
{1=Scala, 2=Python, 3=Java}
Updated on: 30-Mar-2022
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