Flash cards
Review the key moves
1/4
Core idea
What is the main idea behind Java HashMap clone() Method?
Lesson checks
Practice each idea before moving on
Short Mimo-style checks built from this lesson's code, terms, and sequence.
1Quick choice
Which statement best captures the main point of this lesson?
2Fill blank
Complete the missing token from the example code.
___ java.util.HashMap;3Order
Put the learning moves in the order that makes the concept easiest to apply.
The clone() method returns a copy of the map as an Object .
Definition and Usage
Java HashMap clone() Method
❮ HashMap Methods
Example
import java.util.HashMap;
public class Main {
public static void main(String[] args) {
HashMap<String, String> capitalCities = new HashMap<String, String>();
capitalCities.put("England", "London");
capitalCities.put("Germany", "Berlin");
capitalCities.put("Norway", "Oslo");
capitalCities.put("USA", "Washington DC");
HashMap copy = (HashMap)capitalCities.clone();
copy.remove("England");
System.out.println(capitalCities);
System.out.println(copy);
}
}Definition and Usage
The clone() method returns a copy of the map as an Object .
This creates a "shallow" copy, which means that copies of objects in the map are not created, instead the map has references to the same objects that are in the original map.
Note
Since the return type is Object , it must be type casted in order to use it as a HashMap as shown in the example above.
Syntax
public Object clone()Technical Details
| Returns: | A copy of the HashMap object. |
|---|