Java HashMap - computeIfPresent() Method
The java.util.HashMap.computeIfPresent() method is used to update a value in the HashMap, if the specified key is present and non-null. It tries to compute a new mapping given the key and its current mapped value. If the function returns null, the mapping is removed. If the function itself throws an (unchecked) exception, the exception is rethrown, and the current mapping is left unchanged.
Syntax
public V computeIfPresent(
K key,
BiFunction<? super K,? super V,? extends V> remappingFunction
)
Here, K and V are the type of key and value respectively maintained by the container.
Parameters
key |
Specify the key with which the specified value is to be associated. |
remappingFunction |
Specify the function to compute a value. |
Return Value
Returns the new value associated with the specified key, or null if none.
Exception
NA.
Example:
In the example below, the java.util.HashMap.computeIfPresent() method is used to update a value in the given HashMap.
import java.util.*;
public class MyClass {
public static void main(String[] args) {
//creating a HashMap
HashMap<Integer, String> MyMap = new HashMap<Integer, String>();
//populating the HashMap
MyMap.put(101, "John");
MyMap.put(102, "Marry");
MyMap.put(103, "Kim");
MyMap.put(104, "Jo");
//printing the HashMap
System.out.println("MyMap contains: " + MyMap);
//updating value of the specified key using computeIfPresent method
MyMap.computeIfPresent(103, (k, v) -> "Sam");
MyMap.computeIfPresent(104, (k, v) -> "Lee");
//printing the HashMap
System.out.println("MyMap contains: " + MyMap);
}
}
The output of the above code will be:
MyMap contains: {101=John, 102=Marry, 103=Kim, 104=Jo}
MyMap contains: {101=John, 102=Marry, 103=Sam, 104=Lee}
❮ Java.util - HashMap
