What is the LinkedHashMap.clear() method in Java?

The LinkedHashMap class in Java is the same as the HashMap class, except LinkedHashMap maintains the insertion order, whereas HashMap does not.

The LinkedHashMap class uses a doubly-linked list to maintain the insertion order.

You can read more about the LinkedHashMap class here.

What is the clear() method in LinkedHashMap?

The clear() method of the LinkedHashMap class removes all of the key and value mappings from a specified LinkedHashMap object. After calling this method, the LinkedHashMap object becomes empty.

Syntax

public void clear()

This method doesn’t take any parameters and does not return a value.

Code

The code below shows how to use the clear() method.

import java.util.LinkedHashMap;
class LinkedHashMapClearExample {
    public static void main( String args[] ) {
      
      LinkedHashMap<Integer, String> map = new LinkedHashMap<>();
      
      map.put(1, "one");
      map.put(2, "two");
      System.out.println("LinkedHashMap is : "+ map);
      
      map.clear();
      
      System.out.println("\nAfter Calling Clear method");
      System.out.println("\nLinkedHashMap is : " + map);
    }
}

Explanation

In the code above:

  • In line 1, we import the LinkedHashMap class.

  • From lines 5 to 8, we create a LinkedHashMap object and use the put() method to add two mappings ({1=one, 2=two}) to map.

  • In line 11, we use the clear() method to remove all the mappings from map. This makes map empty.

  • In line 14, we print map to ensure that it is empty.

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