How to filter "Null" values from HashMap<String, String>? [duplicate]

Question

Following map, having both key-value pair as String, Write a logic to filter all the null values from Map without using any external API's ?

Is there any other approach than traversing through whole map and filtering out the values (Traversing whole map and getting Entry Object and discarding those pair) ?

        Map<String,String> map = new HashMap<String,String>();          map.put("1", "One");         map.put("2", "Two");         map.put("3", null);         map.put("4", "Four");         map.put("5", null);         //Logic to filer values         //Post filtering It should print only ( 1,2 & 4 pair )   

Answer 1

You can use the Java 8 method Collection.removeIf for this purpose:

map.values().removeIf(Objects::isNull); 

This removed all values that are null.

Online demo

This works by the fact that calling .values() for a HashMap returns a collection that delegated modifications back to the HashMap itself, meaning that our call for removeIf() actually changes the HashMap (this doesn't work on all java Map's)