Question

How to add key-value pair if not exists in a Map with Java

Answer 1

import java.util.Map;
import java.util.Arrays;
import java.util.HashMap;
 
public class MyClass {
    public static void main(String args[]) {
        Map<String, Integer> map = new HashMap<>();
         
        map.put("java", 4);
        map.put("c#", 6);
        map.put("c", 2);
         
        Object[] arr = map.entrySet().toArray();
        System.out.println(Arrays.toString(arr));
        
        map.putIfAbsent("java", 4); 
        map.putIfAbsent("java", 400); 
        map.putIfAbsent("c++", 9);
         
        arr = map.entrySet().toArray();
        System.out.println(Arrays.toString(arr));
    }
}
        
        
        
        
/*
run:
        
[c#=6, java=4, c=2]
[c#=6, c++=9, java=4, c=2]
        
*/

 

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