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Text lesson

replaceAll()

Example

Modify the value of each entry within a map.

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");

    capitalCities.replaceAll((k, v) -> "The capital of " + k + " is " + v);

    System.out.println(capitalCities);
  }
}

Definition and Usage

The replaceAll() method updates the value of each entry in the map by applying an operation using the entry’s key and value. This operation can be defined using a lambda expression compatible with Java’s BiFunction interface’s apply() method.

Syntax

public void replaceAll(BiFunction operator)

Parameter Values

Parameter

Description

operator

Necessary: A BiFunction object or lambda expression operating on each entry.

The function’s first parameter holds the key of an entry, and the second parameter holds its corresponding value.