apache/flink · error · RuntimeException

Could not initialize primitive {} array comparator.

Error message

Could not initialize primitive {} array comparator.

What it means

PrimitiveArrayTypeInfo.createComparator reflectively instantiates the PrimitiveArrayComparator via comparatorClass.getConstructor(boolean.class).newInstance(ascending). If the comparator class lacks the required public boolean constructor or instantiation throws, a RuntimeException names the comparator class with the 'primitive array comparator' suffix. This is an internal contract: each primitive-array comparator must expose that constructor.

Source

Thrown at flink-core/src/main/java/org/apache/flink/api/common/typeinfo/PrimitiveArrayTypeInfo.java:273

    static {
        TYPES.put(boolean[].class, BOOLEAN_PRIMITIVE_ARRAY_TYPE_INFO);
        TYPES.put(byte[].class, BYTE_PRIMITIVE_ARRAY_TYPE_INFO);
        TYPES.put(short[].class, SHORT_PRIMITIVE_ARRAY_TYPE_INFO);
        TYPES.put(int[].class, INT_PRIMITIVE_ARRAY_TYPE_INFO);
        TYPES.put(long[].class, LONG_PRIMITIVE_ARRAY_TYPE_INFO);
        TYPES.put(float[].class, FLOAT_PRIMITIVE_ARRAY_TYPE_INFO);
        TYPES.put(double[].class, DOUBLE_PRIMITIVE_ARRAY_TYPE_INFO);
        TYPES.put(char[].class, CHAR_PRIMITIVE_ARRAY_TYPE_INFO);
    }

    @Override
    @PublicEvolving
    public PrimitiveArrayComparator<T, ?> createComparator(
            boolean sortOrderAscending, ExecutionConfig executionConfig) {
        try {
            return comparatorClass.getConstructor(boolean.class).newInstance(sortOrderAscending);
        } catch (Exception e) {
            throw new RuntimeException(
                    "Could not initialize primitive "
                            + comparatorClass.getName()
                            + " array comparator.",
                    e);
        }
    }
}

View on GitHub (pinned to 2f3c205e92)

Solutions

1. Ensure any custom primitive-array comparator class has a public constructor taking a single boolean.
2. Use the built-in PrimitiveArrayTypeInfo instances rather than custom ones.
3. On restricted JDKs, add the appropriate --add-opens so reflection into the comparator constructor succeeds.

Example fix

// before: custom comparator lacks boolean constructor

// after: ensure public constructor
public class MyIntArrayComparator extends PrimitiveArrayComparator<Integer, IntComparator> {
    public MyIntArrayComparator(boolean ascending) { super(ascending); }
}

try {
    comparatorClass.getConstructor(boolean.class);
} catch (NoSuchMethodException e) {
    throw new IllegalStateException(
        comparatorClass + " must have a public (boolean) constructor", e);
}

static boolean hasBooleanCtor(Class<? extends PrimitiveArrayComparator<?,?>> c) {
    try { c.getConstructor(boolean.class); return true; }
    catch (NoSuchMethodException e) { return false; }
}

try {
    return ti.createComparator(asc, cfg);
} catch (RuntimeException e) {
    throw new IllegalStateException(
        "Primitive array comparator misconfigured: " + comparatorClass, e);
}

When it happens

Trigger: A custom PrimitiveArrayTypeInfo with a comparatorClass missing the (boolean) constructor; reflective access blocked; comparator class made abstract or otherwise non-instantiable in a fork.

Common situations: Forking Flink and altering primitive-array comparators; JDK module restrictions blocking reflective construction; classpath issues loading a partial comparator implementation.

Related errors

• Could not initialize basic comparator {}
• Could not initialize comparator {}
• Could not initialize comparator {}
• The type {} cannot be used as a key.
• The given class is no array.

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/ca92efbb36924846. Report an issue: GitHub.