In this example, we will learn to pass lambda expression as the method argument in Java.
Example 1: Define lambda expressions as method parameters
import java.util.ArrayList; class Main { public static void main(String[] args) { // create an ArrayList ArrayList<String> languages = new ArrayList<>(); // add elements to the ArrayList languages.add("java"); languages.add("swift"); languages.add("python"); System.out.println("ArrayList: " + languages); // pass lambda expression as parameter to replaceAll() method languages.replaceAll(e -> e.toUpperCase()); System.out.println("Updated ArrayList: " + languages); } }
Output
ArrayList: [java, swift, python] Updated ArrayList: [JAVA, SWIFT, PYTHON]
In the above example, we have created an arraylist named languages. Notice the line,
languages.replaceAll(e -> e.toUpperCase());Here, e -> e.toUpperCase() is a lambda expression. It takes all elements of the arraylist and converts them into uppercase.
Example 2: Pass multiline lambda body as function arguments
import java.util.ArrayList; import java.util.Arrays; class Main { public static void main(String[] args) { // create an ArrayList ArrayList<String> languages = new ArrayList<>(Arrays.asList("java", "python")); System.out.println("ArrayList: " + languages); // call the foEach() method // pass lambda as argument fo forEach() // reverse each element of ArrayList System.out.print("Reversed ArrayList: "); languages.forEach((e) -> { // body of lambda expression String result = ""; for (int i = e.length()-1; i >= 0 ; i--) result += e.charAt(i); System.out.print(result + ", "); }); } }
Output
ArrayList: [java, python] Reversed ArrayList: avaj, nohtyp,
In the above example, we have created an arraylist languages. Notice the line,
languages.forEach((e) -> {
// body of lambda expression
String result = "";
for (int i = e.length()-1; i >= 0 ; i--)
result += e.charAt(i);
System.out.print(result + ", ");
});Here, we are passing lambda expression as an argument to the ArrayList forEach() method. The lambda expression will reverse each element of the arraylist.
