Flash cards
Review the key moves
1/4
Core idea
What is the main idea behind Java HashMap replace() 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 replace() method writes a new value to an existing entry in the map.
Definition and Usage
Java HashMap replace() 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", "Cambridge");
capitalCities.put("Germany", "Berlin");
capitalCities.put("Norway", "Oslo");
capitalCities.put("USA", "Washington DC");
capitalCities.replace("England", "London");
capitalCities.replace("Canada", "Ottawa");
capitalCities.replace("USA", "New York", "Washington DC");
System.out.println(capitalCities);
}
}Definition and Usage
The replace() method writes a new value to an existing entry in the map. The entry can be specified by its key, or by both its key and value.
One of the following
public V replace(K
key , V
newValue )public boolean replace(K
key , V
oldValue , V
newValue )K and V refer to the data types of the keys and values of the map.
Parameter Values
| Parameter | Description |
|---|---|
| key | Required. The key of the entry to be removed. |
| oldValue | Optional. The value of the entry to be removed. |
| newValue | Required. The value to write into the entry. |
Technical Details
| Returns: | When the oldValue argument is specified, it returns true if the entry was replaced and false otherwise. If the oldValue argument is not specified then it returns the value that the entry had before it was replaced, or null if an entry with the specified key does not exist. |
|---|