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How to use null value as key in Java HashMap
Yes, you can set null as key in Java HashMap. For this, let’s first create a HashMap with key and value pair −
Map<String,String>map = new HashMap<>();
map.put("Football", "A");
map.put("Squash", "B");
map.put("Cricket", "C");
map.put("Hockey", "D");
map.put("Rugby", "E");Now, let’s add null value as key −
map.put(null, "H");
You can try to get the value for key as “null” −
map.get(null);
Example
import java.util.HashMap;
import java.util.Map;
public class Demo {
public static final void main(String[] args) {
Map<String,String>map = new HashMap<>();
map.put("Football", "A");
map.put("Squash", "B");
map.put("Cricket", "C");
map.put("Hockey", "D");
map.put("Rugby", "E");
map.put("Golf", "F");
map.put("Archery", "G");
System.out.println("Size of HashMap = " + map.size());
map.put(null, "H");
System.out.println("Updated Size of HashMap = " + map.size());
System.out.println("For null = " + map.get(null));
}
}Output
Size of HashMap = 7 Updated Size of HashMap = 8 For null = H
Updated on: 30-Jul-2019
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