Question

How to add value to HashMap if key not exists in Java

Answer 1

import java.util.HashMap;
import java.util.Map.Entry;
 
public class MyClass {
    public static void main(String args[]) {
        HashMap<String, Integer> hashmap = new HashMap<>();
 
        hashmap.put("java", 1);
        hashmap.put("c", 2);
        hashmap.put("c++", 3);
        hashmap.put("python", 4);
 
        for (Entry<String, Integer> pair : hashmap.entrySet()) {
            System.out.println(pair.getKey() + " : " + pair.getValue());
        }
        
        hashmap.putIfAbsent("java", 111);
        hashmap.putIfAbsent("swift", 222);
        
        System.out.println();
        for (Entry<String, Integer> pair : hashmap.entrySet()) {
            System.out.println(pair.getKey() + " : " + pair.getValue());
        }
    }
}
 
 
 
 
/*
run:
 
c++ : 3
python : 4
java : 1
c : 2

c++ : 3
python : 4
java : 1
c : 2
swift : 222
 
*/

 

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