Question

How to create a method that takes a lambda expression as a parameter in Java

Answer 1

interface StringFunction {
  String run(String str);
}

public class Main {
  public static void main(String[] args) {
    StringFunction num24 = (s) -> s + "24";
    StringFunction num25 = (s) -> s + "25";
    
    printFormatted("Java", num24);
    printFormatted("Java", num25);
  }
  public static void printFormatted(String str, StringFunction format) {
    String result = format.run(str);

    System.out.println(result);
  }
}


/*
run:

Java24
Java25

*/

 

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Answer 2

import java.util.function.Consumer;

public class Main {
    // Method that accepts a lambda expression as a parameter
    public static void processList(int[] numbers, Consumer<Integer> action) {
        for (int num : numbers) {
            action.accept(num); // Apply the lambda action to each element
        }
    }

    public static void main(String[] args) {
        int[] numbers = {1, 2, 3, 4, 5, 6};

        // Passing a lambda expression to print each number
        processList(numbers, num -> System.out.println("Number: " + num));
        
        System.out.println();

        // Passing a lambda expression to double each number and print it
        processList(numbers, num -> System.out.println("Double Number: " + (num * 2)));
    }
}


/*
run:

Number: 1
Number: 2
Number: 3
Number: 4
Number: 5
Number: 6

Double Number: 2
Double Number: 4
Double Number: 6
Double Number: 8
Double Number: 10
Double Number: 12

*/

 

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