Java TreeMap - remove() Method

The java.util.TreeMap.remove() method is used to remove the mapping for the specified key from this map if present.

Syntax

public V remove(Object key)

Here, V is the type of value maintained by the container.

Parameters

Return Value

Returns the previous value associated with key, or null if there was no mapping for key. (A null return can also indicate that the map previously associated null with key.)

Exception

• Throws ClassCastException, if the specified key cannot be compared with the keys currently in the map.
• Throws NullPointerException, if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys.

Example:

In the example below, the java.util.TreeMap.remove() method is used to remove the mapping for the specified key from the given map.

import java.util.*;

public class MyClass {
  public static void main(String[] args) {
    //creating a treemap
    TreeMap<Integer, String> MyMap = new TreeMap<Integer, String>();

    //populating the map
    MyMap.put(101, "John");
    MyMap.put(102, "Marry");
    MyMap.put(103, "Kim");
    MyMap.put(104, "Jo");

    //printing the map
    System.out.println("Before remove, MyMap contains: " + MyMap);    

    //remove mapping for 102 key
    MyMap.remove(102); 

    //printing the map
    System.out.println("After remove, MyMap contains: " + MyMap);  
  }
}

The output of the above code will be:

Before remove, MyMap contains: {101=John, 102=Marry, 103=Kim, 104=Jo}
After remove, MyMap contains: {101=John, 103=Kim, 104=Jo}