Issue refactoring Java if-for loop-if to if-stream

ghz 8months ago ⋅ 53 views
  • Include details about your goal

I wish to refactor the below code using Java stream()

    public String before(String input) {
        if (input.contains("to for loop")) {
            String[] splitBySpace = input.split(" ");
            for (String s : splitBySpace) {
                if (s.contains("a:")) {
                    String[] anotherSplit = s.split(":");
                    return anotherSplit[1];
                }
            }
        }
        return null;
    }
  • What I tried:
    public String after(String input) {
        if (input.contains("to for loop")) {
            String[] splitBySpace = input.split(" ");
            return Arrays.stream(splitBySpace)
.filter(oneSplit -> oneSplit.contains("a:"))
.map(oneContains -> oneContains.split(";")[1])
.findFirst();
        }
        return null;
    }
  • Issue:

Unfortunately, the refactored method is giving an Optional of String, instead of the String, cannot compile.

  • Question?

What is the correct refactored method using Java stream?

Answers

To correctly refactor the method using Java Stream API, you need to handle the case where the findFirst() operation returns an Optional. You can either modify the method to return an Optional<String> or extract the value from the Optional using orElse(null) if you still want to return null in case of no match. Here's how you can do it:

Option 1: Returning an Optional<String>:

import java.util.Arrays;
import java.util.Optional;

public Optional<String> after(String input) {
    if (input.contains("to for loop")) {
        String[] splitBySpace = input.split(" ");
        return Arrays.stream(splitBySpace)
                .filter(oneSplit -> oneSplit.contains("a:"))
                .map(oneContains -> oneContains.split(":")[1])
                .findFirst();
    }
    return Optional.empty();
}

Option 2: Extracting value from Optional:

import java.util.Arrays;

public String after(String input) {
    if (input.contains("to for loop")) {
        String[] splitBySpace = input.split(" ");
        return Arrays.stream(splitBySpace)
                .filter(oneSplit -> oneSplit.contains("a:"))
                .map(oneContains -> oneContains.split(":")[1])
                .findFirst()
                .orElse(null);
    }
    return null;
}

Both options achieve the same result. Option 1 returns an Optional<String> directly, allowing the caller to handle the presence or absence of a result more explicitly. Option 2 extracts the value from the Optional using orElse(null), providing a similar behavior to the original method. You can choose the option that fits your use case better.

#issue