javaLogic errorMedium

Boxed Long equality comparison outside cache range

Time: 0:00

BugFind the bug and fix the code

What it should do

Check if two boxed Long values represent the same number. Example: compareBoxedLongs(1000, 1000) -> true

What happens instead

Long == Long evaluates to false for numbers outside the -128 to 127 cache range

public class Main {
    public static boolean compareBoxedLongs(long a, long b) {
        Long valA = a;
        Long valB = b;
        // == compares object references; outside -128..127 they are distinct heap objects
        return valA == valB;
    }

    public static void main(String[] args) {
        System.out.println(compareBoxedLongs(1000, 1000));
    }
}

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

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This bug belongs to the logic errors pattern

The wrong operator, an inverted condition, a formula the right way round but backwards.

Learn the logic errors pattern Step through your own code

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public class Main { public static boolean compareBoxedLongs(long a, long b) { Long valA = a; Long valB = b; // == compares object references; outside -128..127 they are distinct heap objects return valA == valB; } public static void main(String[] args) { System.out.println(compareBoxedLongs(1000, 1000)); } }

Boxed Long equality comparison outside cache range

What it should do

What happens instead

More logic errors to practise

Boxed Long equality comparison outside cache range

What it should do

What happens instead

More logic errors to practise