Java HashMap replace() Method
Java HashMapThe replace() method replaces the value corresponding to the specified key in the hashMap.
The syntax of the replace() method is:
hashmap.replace(K key, V newValue) 或 hashmap.replace(K key, V oldValue, V newValue)
Note:hashmap is an object of the HashMap class.
Parameter details:
- key - the key
- oldValue - the old value
- newValue - the new value
Return Value
If oldValue is not present, replace the value corresponding to key and return the old value corresponding to key; if oldValue is present, return true upon successful replacement; if key does not exist, return null.
Example
The following example demonstrates the use of the replace() method:
Example
import java.util.HashMap;
class Main {
public static void main(String[] args) {
// Create a HashMap
HashMap<Integer, String> sites = new HashMap<>();
// Add some elements to the HashMap
sites.put(1, "Google");
sites.put(2, "Example");
sites.put(3, "Taobao");
System.out.println("sites HashMap: " + sites);
// Replace the mapping with key 2
String value = sites.replace(2, "Wiki");
System.out.println("Replaced Value: " + value);
System.out.println("Updated HashMap: " + sites);
}
}
class Main {
public static void main(String[] args) {
// Create a HashMap
HashMap<Integer, String> sites = new HashMap<>();
// Add some elements to the HashMap
sites.put(1, "Google");
sites.put(2, "Example");
sites.put(3, "Taobao");
System.out.println("sites HashMap: " + sites);
// Replace the mapping with key 2
String value = sites.replace(2, "Wiki");
System.out.println("Replaced Value: " + value);
System.out.println("Updated HashMap: " + sites);
}
}
Executing the above program produces the following output:
Replaced Value: Example
Updated HashMap: {1=Google, 2=Wiki, 3=Taobao}
HashMap replace() method with old value:
Example
import java.util.HashMap;
class Main {
public static void main(String[] args) {
// Create a HashMap
HashMap<Integer, String> sites = new HashMap<>();
// Add some elements to the HashMap
sites.put(1, "Google");
sites.put(2, "Example");
sites.put(3, "Taobao");
System.out.println("sites HashMap: " + sites);
// Replace the mapping {1 = Google}; perform the replacement
sites.replace(1, "Google", "Wiki"); // Returns true
// The mapping {2 = Weibo} does not exist, so no operation is performed
sites.replace(2, "Weibo", "Zhihu"); // Returns false
System.out.println("sites after replace():\n" + sites);
}
}
class Main {
public static void main(String[] args) {
// Create a HashMap
HashMap<Integer, String> sites = new HashMap<>();
// Add some elements to the HashMap
sites.put(1, "Google");
sites.put(2, "Example");
sites.put(3, "Taobao");
System.out.println("sites HashMap: " + sites);
// Replace the mapping {1 = Google}; perform the replacement
sites.replace(1, "Google", "Wiki"); // Returns true
// The mapping {2 = Weibo} does not exist, so no operation is performed
sites.replace(2, "Weibo", "Zhihu"); // Returns false
System.out.println("sites after replace():\n" + sites);
}
}
Executing the above program produces the following output:
sites HashMap: {1=Google, 2=Example, 3=Taobao}
sites after replace():
{1=Wiki, 2=Example, 3=Taobao}
Other extensions