Question

How to store multiple values under the same key in a HashMap with Java

Answer 1

import java.util.HashMap;
import java.util.List;

public class User {
    public static void main(String args[]) {
        HashMap<String, List<String>> map = new HashMap<>();
        
        map.put("key1", List.of("value1", "value2", "value3"));
        map.put("key2", List.of("value4", "value5", "value6"));

        for (String key : map.keySet()) {
            System.out.println(key + ": " + map.get(key));
        }
     }
}
    
    
    
    
/*
run:
    
key1: [value1, value2, value3]
key2: [value4, value5, value6]
  
*/

 

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Answer 2

import java.util.HashMap;

public class User {
    public static void main(String args[]) {
        HashMap<String, String[]> map = new HashMap<>();
        
        map.put("key1", new String[] {"value1", "value2", "value3"});
        map.put("key2", new String[] {"value4", "value5", "value6"});

        for (String key : map.keySet()) {
            System.out.println(key + ": " + String.join(", ", map.get(key)));
        }
     }
}
    
    
    
    
/*
run:
    
key1: value1, value2, value3
key2: value4, value5, value6
  
*/

 

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