10 ChatGPT Prompts Every Java Developer Should Use to Optimize Their Code (With Examples)

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If you are a Java developer, you’ve probably faced this situation:
Your code works… but it’s slow, memory-hungry, or just plain messy.

The good news? With the right prompts, ChatGPT can act like your personal code reviewer, performance tuner, and refactoring assistant — all rolled into one.

1. Refactor for Performance

Prompt:
“Here’s my Java method: [paste code]. Can you refactor it for better performance without changing its functionality?”

Before:

public int sumList(List<Integer> numbers) {
    int sum = 0;
    for (int i = 0; i < numbers.size(); i++) {
        sum += numbers.get(i);
    }
    return sum;
}

After:

public int sumList(List<Integer> numbers) {
    return numbers.stream().mapToInt(Integer::intValue).sum();
}