javaScope errorMedium

Resource leak due to missing try-with-resources

Time: 0:00

BugFind the bug and fix the code

What it should do

Read string scanner words and return count. Example: readStreamWordCount("hello world") -> 2

What happens instead

Resource leak warning: Scanner is never closed if an exception occurs during reading

import java.util.Scanner;

public class Main {
    public static int readStreamWordCount(String input) {
        Scanner scanner = new Scanner(input);
        int count = 0;
        while (scanner.hasNext()) {
            scanner.next();
            count++;
        }
        // If an exception occurs, scanner is never closed
        return count;
    }

    public static void main(String[] args) {
        System.out.println(readStreamWordCount("hello world"));
    }
}

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 scope and closure bugs pattern

Every callback reports the last value, a counter never increments, UnboundLocalError on a variable you can see.

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import java.util.Scanner; public class Main { public static int readStreamWordCount(String input) { Scanner scanner = new Scanner(input); int count = 0; while (scanner.hasNext()) { scanner.next(); count++; } // If an exception occurs, scanner is never closed return count; } public static void main(String[] args) { System.out.println(readStreamWordCount("hello world")); } }

Resource leak due to missing try-with-resources

What it should do

What happens instead

More scope and closure bugs to practise

Resource leak due to missing try-with-resources

What it should do

What happens instead

More scope and closure bugs to practise