Auto-suggest StringBuilder optimizations

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创建于 2025年11月18日 09:54

IntelliJ makes many suggestions for improving efficiency. It would be nice if this included suggesting replacing:

stringBuilder.append(string.substring(start, end))

with the more efficient:

stringBuilder.append(string, start, end)

3 条评论

Alyona Zaslavskaya

创建于 2025年11月20日 13:29

正式评论

Hi Derektom14,

Thanks for the clarification about Kotlin!

I was able to reproduce a lack of quick fix suggestion you observed and created a ticket KTIJ-36533 for the team to take a further look at it. Fell free to follow it to get updates on its progress.

Aram Leblebjian

创建于 2025年11月18日 11:21

Hi Derektom14.

I tried reproducing your case with the following code:

public class Main {
    public static void main(String[] args) {
        StringBuilder sb = new StringBuilder();
        String str = "Hello World";
        int start = 0;
        int end = 5;
        sb.append(str.substring(start, end));
    }
}

In my environment, IntelliJ IDEA correctly suggests: “Call to substring() is redundant” and offers to replace it with sb.append(str, start, end) (Check the attached screenshots).

I am currently using IntelliJ IDEA 2025.2.4, and the suggestion is working as expected. If you’re on an older build, I recommend upgrading to the latest IntelliJ IDEA release.

Derektom14

创建于 2025年11月19日 02:11

Ah, I'm also using 2025.2.4 and get the same correction suggestion in Java, but not in Kotlin. Does the suggestion need to be updated to also accommodate Kotlin? If so, I expect many other suggestions to need similar updates.

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