Java 8 Map Sorting Example Code

import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;

public class Java8SortMapDemo {

    public static void main(String[] args) {
        // Create a Map object of type <String, String> and adding key-value pairs
        Map<String,String> ceo = new HashMap<>();
        ceo.put("Google", "Sundar Pichai");
        ceo.put("Facebook", "Mark Zuckerberg");
        ceo.put("Twitter", "Jack Dorsey");
        ceo.put("Apple", "Tim Cook");
        ceo.put("Microsoft", "Satya Nadella");
        ceo.put("Amazon", "Jeff Bezos");
        ceo.put("Oracle", "Mark Hurd");
        ceo.put("SpaceX", "Elon Musk");

        // Iterating Original Map
        System.out.println("Original Map: \n" + ceo);
        System.out.println();
        
        // Sort Map by Key
        sortMapByKey(ceo);

        System.out.println();

        // Sort Map by Value
        sortMapByValue(ceo);

        System.out.println();

        // Sort Map by Key in Reverse Order
        sortMapByKeyInReverseOrder(ceo);

        System.out.println();

        // Sort Map by Value in Reverse Order
        sortMapByValueInReverseOrder(ceo);
    }

    private static void sortMapByKey(Map<String, String> ceo) {
        // Creating LinkedHashMap for sorting entries after SORTING by keys using Stream in Java8
        Map<String, String> keyMap = new LinkedHashMap<>();
        // Sorting by Kyes using the 'comparingByKey()' method
        ceo.entrySet().stream().sorted(Map.Entry.comparingByKey()).forEachOrdered(c -> keyMap.put(c.getKey(), c.getValue()));
        
        System.out.println("Map Sorting by Key : \n " + keyMap);
    }
    
    private static void sortMapByValue(Map<String, String> ceo) {
        // Creating LindedHashMap for sorting entries after SORTING by Values using Stream in Java8
        Map<String, String> valueMap = new LinkedHashMap<>();
        // Sorting by Value using the 'comparingByValue()' method
        ceo.entrySet().stream().sorted(Map.Entry.comparingByValue()).forEachOrdered(c -> valueMap.put(c.getKey(), c.getValue()));
        
        System.out.println("Map Sorted by Value : \n " + valueMap);
    }
    
    private static void sortMapByKeyInReverseOrder(Map<String, String> ceo) {
        // Creating LinkedhashMap for storing entries after SORTING by Keys using Stream in Java8
        Map<String, String> keyRMap = new LinkedHashMap<>();
        // Sorting by keys using the 'comparingByKey()' method
        ceo.entrySet().stream().sorted(Collections.reverseOrder(Map.Entry.comparingByKey())).forEachOrdered(c -> keyRMap.put(c.getKey(), c.getValue()));
        
        System.out.println("Map Sorted by Key in Reverse order : \n " + keyRMap);
    }
    
    private static void sortMapByValueInReverseOrder(Map<String, String> ceo) {
        // Creating LinkedhashMap for storing entries after SORTING by Values using Stream in Java8
        Map<String, String> valueMap = new LinkedHashMap<>();
        // Sorting by Keys using the 'comparingByKey()' method
        ceo.entrySet().stream().sorted(Collections.reverseOrder(Map.Entry.comparingByValue())).forEachOrdered(c -> valueMap.put(c.getKey(), c.getValue()));

        System.out.println("Map Sorted by Value in Reverse order : \n " + valueMap);
    }
    
}
Jeonguk Lee

Java 8 Map Sorting

Java 8 Map Sorting Example Code

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