@Override
    protected StateFactory<MaxAggregatorState> init(ExpressionExecutor[] attributeExpressionExecutors,
                                                    ProcessingMode processingMode,
                                                    boolean outputExpectsExpiredEvents,
                                                    ConfigReader configReader,
                                                    SiddhiQueryContext siddhiQueryContext) {
        if (attributeExpressionExecutors.length != 1) {
            throw new OperationNotSupportedException("Max aggregator has to have exactly 1 parameter, currently " +
                    attributeExpressionExecutors.length + " parameters provided");
        }
        boolean trackFutureStates = false;
        if (processingMode == ProcessingMode.SLIDE || outputExpectsExpiredEvents) {
            trackFutureStates = true;
        }
        attributeExpressionExecutor = attributeExpressionExecutors[0];
        returnType = attributeExpressionExecutors[0].getReturnType();
        boolean finalTrackFutureStates = trackFutureStates;
        return () -> {
            switch (returnType) {
                case FLOAT:
                    return new MaxAttributeAggregatorStateFloat(finalTrackFutureStates);
                case INT:
                    return new MaxAttributeAggregatorStateInt(finalTrackFutureStates);
                case LONG:
                    return new MaxAttributeAggregatorStateLong(finalTrackFutureStates);
                case DOUBLE:
                    return new MaxAttributeAggregatorStateDouble(finalTrackFutureStates);
                default:
                    throw new OperationNotSupportedException("Max not supported for " + returnType);
            }
        };
    }
The initialization method for FunctionExecutor

@param attributeExpressionExecutors are the executors of each attributes in the function
@param processingMode               query processing mode
@param outputExpectsExpiredEvents   is expired events sent as output
@param configReader                 this hold the {@link MaxAttributeAggregatorExecutor} configuration reader.
@param siddhiQueryContext           Siddhi query runtime context
modules/siddhi-core/src/main/java/io/siddhi/core/query/selector/attribute/aggregator/MaxAttributeAggregatorExecutor.java