microg/GmsCore · error · IllegalArgumentException

Not a double type

Error message

Not a double type

What it means

Flag.getDouble() throws IllegalArgumentException("Not a double type") when the flag's dataType is not DATA_TYPE_DOUBLE. Each typed accessor in Flag validates the dataType discriminator before returning its field, so reading the double field of a flag that is not of double type fails fast instead of returning an undefined value.

Source

Thrown at play-services-phenotype/src/main/java/com/google/android/gms/phenotype/Flag.java:83

        this.flagType = flagType;
    }

    public long getLong() {
        if (dataType == DATA_TYPE_LONG)
            return longValue;
        throw new IllegalArgumentException("Not a long type");
    }

    public boolean getBool() {
        if (dataType == DATA_TYPE_BOOL)
            return boolValue;
        throw new IllegalArgumentException("Not a boolean type");
    }

    public double getDouble() {
        if (dataType == DATA_TYPE_DOUBLE)
            return doubleValue;
        throw new IllegalArgumentException("Not a double type");
    }

    public String getString() {
        if (dataType == DATA_TYPE_STRING)
            return stringValue;
        throw new IllegalArgumentException("Not a String type");
    }

    public byte[] getBytes() {
        if (dataType == DATA_TYPE_BYTES)
            return bytesValue;
        throw new IllegalArgumentException("Not a bytes type");
    }

    public static final int DATA_TYPE_LONG = 1;
    public static final int DATA_TYPE_BOOL = 2;
    public static final int DATA_TYPE_DOUBLE = 3;
    public static final int DATA_TYPE_STRING = 4;

View on GitHub (pinned to 157c9d86ac)

Solutions

1. Check flag.getDataType() == Flag.DATA_TYPE_DOUBLE before calling getDouble()
2. If numeric values may be long, accept DATA_TYPE_LONG and widen to double via ((double) flag.getLong())
3. Switch over DATA_TYPE_* constants and handle each typed case
4. Verify the server-side flag type is still double

Example fix

// before
double d = flag.getDouble();
// after
double d;
if (flag.getDataType() == Flag.DATA_TYPE_DOUBLE) d = flag.getDouble();
else if (flag.getDataType() == Flag.DATA_TYPE_LONG) d = (double) flag.getLong();
else d = 0.0;

if (flag.getDataType() != Flag.DATA_TYPE_DOUBLE) { throw new IllegalStateException("flag is not a double: " + flag.getDataType()); }

static boolean isDoubleFlag(Flag f) { return f != null && f.getDataType() == Flag.DATA_TYPE_DOUBLE; }

try { double v = flag.getDouble(); } catch (IllegalArgumentException e) { log.warn("Flag type mismatch", e); v = DEFAULT_DOUBLE; }

When it happens

Trigger: Calling Flag.getDouble() on a Flag whose dataType is DATA_TYPE_LONG (1), DATA_TYPE_BOOL (2), DATA_TYPE_STRING (4), or DATA_TYPE_BYTES (5) instead of DATA_TYPE_DOUBLE (3).

Common situations: Server experiment changed a flag from double to long or string; generic flag-parsing code that assumes a fixed type per field; migrating from another config library where numbers were uniformly doubles.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

• Not a long type
• Not a boolean type
• Not a String type
• Not a bytes type
• remoteBinder is the wrong class.

AI-assisted analysis of microg/GmsCore@157c9d86ac (2026-09-06). Data as JSON: /api/errors/f84fc2acc489d732. Report an issue: GitHub.