I want to get an element (NOT the index) from a Java list using a callback.

In JavaScript, there is the Array.prototype.find method that does exactly that. For example:

let match = [1, 2, 3, 4, 5].find((num) => num === 3);
console.log(match); // 3

Is there a Java equivalent?

I want to get an element (NOT the index) from a Java list using a callback.

In JavaScript, there is the Array.prototype.find method that does exactly that. For example:

let match = [1, 2, 3, 4, 5].find((num) => num === 3);
console.log(match); // 3

Is there a Java equivalent?

• javascript
• java
• list
• arraylist

• 1 Are you trying to find the index or trying to find the element 3? If you're looking for 3 why would you return 3? Wouldn't you just want to know if it exists or not? – Jason Commented Apr 9, 2020 at 14:42
• Hi. i want the element, NOT the index. – ryanwaite28 Commented Apr 9, 2020 at 14:48
• 4 Does this answer your question? Java - Find Element in Array using Condition and Lambda – Savior Commented Apr 9, 2020 at 14:51

5 Answers 5

You can do so using Java Stream API.

import java.util.List;

public class Main {
    public static void main(String[] args) {
        int x = List.of(10, 20, 30, 40, 50).stream().filter(n -> (n == 30)).findAny().orElse(-1);
        System.out.println(x);
        int y = List.of(10, 20, 30, 40, 50).stream().filter(n -> (n == 3)).findAny().orElse(-1);
        System.out.println(y);
    }
}

Output:

30
-1

Use findAny() or findFirst() depending on your requirement.

You can do the same in Java using lamda function:

 Optional<Integer> result = Arrays.stream (array).filter(num -> (num==3)).findAny();
 result.ifPresent(num -> System.out.println(name));

Have you tried

list.stream().filter(n -> n == 3 ).findFirst().ifPresent(n -> doSomething(n))

?

If you're trying to determine if a number exists in an array or collection you can simply use IntStream#filter.

int value = IntStream.of(1, 2, 3, 4, 5).filter(v -> v == 3).findAny().orElse(-1);

I Kinda found what i was looking for on this site - https://www.baeldung./find-list-element-java

Basically this:

Object item = someList
  .stream()
  .filter(i -> i.getName().equalsIgnoreCase(name))
  .findAny()
  .orElse(null); 

if (item != null) {
  // ...
}