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About Ilias Tsagklis

Ilias Tsagklis
Ilias is a software developer turned online entrepreneur. He is co-founder and Executive Editor at Java Code Geeks.

Remove all mappings from HashMap example

This is an example of how to remove all mappings from a HashMap, that means removing all key value pairs in a HashMap. Removing all key value pairs from a HashMap implies that you should:

  • Create a new HashMap.
  • Populate the hashMap with elements, with the put(K key, V value) API method of HashMap.
  • Invoke the clear() API method of HashMap, to remove all mappings of the hashMap. The map will be empty after this call returns.

Let’s take a look at the code snippet that follows:

package com.javacodegeeks.snippets.core;

import java.util.HashMap;
 
public class ClearHashMap {
 
  public static void main(String[] args) {
 
    // Create a HashMap and populate it with elements
    HashMap hashMap = new HashMap();
    hashMap.put("key_1","value_1");
    hashMap.put("key_2","value_2");
    hashMap.put("key_3","value_3");
 
    System.out.println("HashMap contains : " + hashMap);

    // void clear method() removes all mappings of HashMap class
    hashMap.clear();

    System.out.println("HashMap contains : " + hashMap);
  }
}

Output:

HashMap contains : {key_3=value_3, key_2=value_2, key_1=value_1}
HashMap contains : {}

 
This was an example of how to remove all mappings from a HashMap in Java.

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