MuntashirAkon/AppManager · error · IllegalArgumentException

buffersize must be bigger than 0

Error message

buffersize must be bigger than 0

What it means

IOUtils.copy(InputStream,OutputStream,int) allocates a byte[buffersize] transfer buffer and rejects buffersize < 1 with IllegalArgumentException, since a zero/negative buffer can never be allocated or used for reads.

Solutions

  1. Pass a positive buffersize, e.g. 8192 (8 KB, a common default)
  2. Validate/clamp the configured buffer size before calling
  3. Use the two-argument IOUtils.copy(input, output) overload which picks a sane default

Example fix

// before
IOUtils.copy(in, out, bufferSize); // bufferSize == 0
// after
IOUtils.copy(in, out, Math.max(1, bufferSize));
Defensive patterns

Strategy: validation

Validate before calling

if (buffersize < 1) throw new IllegalArgumentException("buffersize must be >= 1");

Try / catch

try { IOUtils.copy(in, out, size); } catch (IllegalArgumentException e) { if (e.getMessage().contains("buffersize")) { IOUtils.copy(in, out, 8192); } else throw e; }

Prevention

When it happens

Trigger: Calling IOUtils.copy(input, output, 0) or with a negative buffersize, e.g. passing a user-configured chunk size that defaulted to 0 or a subtraction that yielded <= 0.

Common situations: Config file with buffersize=0; integer arithmetic overflow/underflow computing the size; copying the two-arg copy() signature but adding 0 as buffer size.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

AI-assisted analysis of MuntashirAkon/AppManager@0152f468fc (2026-09-12). Data as JSON: /api/errors/7a9d37f53ae728ea. Report an issue: GitHub.

Appendix: source

Thrown at app/src/main/java/org/apache/commons/compress/utils/IOUtils.java:66

    /**
     * Copies the content of a InputStream into an OutputStream
     *
     * @param input
     *            the InputStream to copy
     * @param output
     *            the target Stream
     * @param buffersize
     *            the buffer size to use, must be bigger than 0
     * @return the number of bytes copied
     * @throws IOException
     *             if an error occurs
     * @throws IllegalArgumentException
     *             if buffersize is smaller than or equal to 0
     */
    public static long copy(final InputStream input, final OutputStream output, final int buffersize) throws IOException {
        if (buffersize < 1) {
            throw new IllegalArgumentException("buffersize must be bigger than 0");
        }
        final byte[] buffer = new byte[buffersize];
        int n = 0;
        long count=0;
        while (-1 != (n = input.read(buffer))) {
            output.write(buffer, 0, n);
            count += n;
        }
        return count;
    }

    /**
     * Skips the given number of bytes by repeatedly invoking skip on
     * the given input stream if necessary.
     *
     * <p>In a case where the stream's skip() method returns 0 before
     * the requested number of bytes has been skip this implementation
     * will fall back to using the read() method.</p>

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