TreeMap Internal Working

Internal working of Tree Map: -

TreeMap doesn’t use Hashing like HashMap. It uses RED BLACK Tree data structure.

Each node in tree will have three references i.e. its parent, right and left element.

·         The left element will always be less than parent.

·         The right element will always be greater than OR equal to parent.

The comparison of Objects is done by natural order using comparable interface.

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Here we can insert multiple null values, but no null keys, if we insert null key that it will throw NullPointer exception.

package test;

import java.util.Map;

import java.util.TreeMap;

public class MainTest {

       public static void main(String... args) throws Exception {

              Map<Integer, String> treeMap = new TreeMap<>();

              treeMap.put(1, null);

              treeMap.put(5, null);

              treeMap.put(3, null);

       }

}