What causes "Couldn't read number!" in Tencent/matrix?

Catch ParseException and skip this sampling round, then retry next tick.

Tencent/matrix · error · ProcStatUtil.ParseException

Couldn't read number!

Error message

Couldn't read number!

What it means

ProcStatReader.readNumber() accumulates digits into a number; if the first character is neither a digit nor '-' it cannot parse a numeric token and throws ParseException("Couldn't read number!"). Called by jiffies(), it means the expected utime/stime numeric field did not start with a number.

Solutions

Catch ParseException and skip this sampling round, then retry next tick.
Verify field alignment: ensure comm (in parentheses, possibly containing spaces/digits) is consumed correctly before reading utime/stime.
Use ProcStatUtil.parseWithBuffer which tokenizes from the raw byte array and handles the comm field explicitly.
Sanity-check the raw /proc/<pid>/stat line on the failing device.

Example fix

// before
long jiffies = ProcStatUtil.instance.jiffies(pid, true);
// after
Long jiffies = null;
try {
    jiffies = ProcStatUtil.instance.jiffies(pid, true);
} catch (ProcStatUtil.ParseException e) {
    // skip malformed sample
}

Defensive patterns

Strategy: try-catch

Validate before calling

// verify stat line field alignment after comm
String line = readStatLine(pid);
int close = line.lastIndexOf(')');
String[] rest = line.substring(close + 2).trim().split("\\s+");
boolean ok = rest.length >= 2 && rest[11].matches("\\d+"); // utime at index 11 after state

Try / catch

try { long j = ProcStatUtil.instance.jiffies(pid, true); } catch (ProcStatUtil.ParseException e) { j = -1; /* skip */ }

Prevention

Ensure comm is parsed via parentheses, not whitespace splitting
Validate one stat line format per device before enabling sampling
Catch ParseException per-pid inside the sampling loop
Update Matrix if stat layout errors recur on specific kernels

When it happens

Trigger: Calling jiffies() when the current position lands on a non-digit, non-'-' character on the first iteration - e.g. field offsets shifted by an unusual comm value or an unexpected stat layout.

Common situations: Kernel variations or emulators where field ordering differs; a prior mis-parse of the parenthesized process name (comm) leaving the reader positioned inside text.

Understand the failure class

Background: "failed to read file", EACCES, ENOENT and "could not read <path>" errors: when a program can't read a file from disk — this error's family across 49 libraries.

Related errors

AI-assisted analysis of Tencent/matrix@3b8293bd65 (2026-09-08). Data as JSON: /api/errors/e87af6a78c6c7b18. Report an issue: GitHub.

Appendix: source

Thrown at matrix/matrix-android/matrix-battery-canary/src/main/java/com/tencent/matrix/batterycanary/utils/ProcStatReader.java:175

        buffer.flip();
        return buffer;
    }

    public long readNumber() {
        long sign = 1;
        long result = 0;
        boolean isFirstRun = true;

        while (hasNext()) {
            next();
            if (Character.isDigit(mChar)) {
                result = result * 10 + (mChar - '0');
            } else if (isFirstRun) {
                if (mChar == '-') {
                    sign = -1;
                } else {
                    throw new ParseException("Couldn't read number!");
                }
            } else {
                rewind();
                break;
            }

            isFirstRun = false;
        }

        if (isFirstRun) {
            throw new ParseException("Couldn't read number because the file ended!");
        }

        return sign * result;
    }

    public CharBuffer readToSymbol(char symbol, CharBuffer buffer) {
        buffer.clear();

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