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Java Program Sorts Map by Key

Comprehensive Java Examples

In this example, we will learn how to sort the map by keys in Java.

To understand this example, you should know the followingJava ProgrammingTopic:

Example: Use TreeMap to sort the map by key

Example

import java.util.HashMap;
import java.util.Map;
import java.util.TreeMap;
class Main {
　　public static void main(String[] args) {
　　　　//Create a hashmap
　　　　Map<String, String> languages = new HashMap<>();
　　　　languages.put("pos3",　"JS");
　　　　languages.put("pos1",　"Java");
　　　　languages.put("pos2",　"Python");
　　　　System.out.println("Map:　"　+　languages);
　　　　//Create TreeMap from map
　　　　TreeMap<String,　String>　sortedNumbers　=　new　TreeMap<>(languages);
　　　　System.out.println("Map with sorted keys"　+　sortedNumbers);
　　}
}

Output Result

Map:　{pos1=Java,　pos2=Python,　pos3=JS}
Map with sorted keys {pos1=Java,　pos2=Python,　pos3=JS}

In the above example, we used HashMap to create a map named planguages. Here, the map is not sorted.

To sort the map, we created a TreeMap from the map. Now, the map is sorted by its keys.