State experimental Pattern

StatePattern.java

package com.sham.vinicius.fiorin;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.Getter;

import java.math.BigDecimal;
import java.util.List;

/**
 * Single class State with Visitor pattern
 */
public class StatePattern {

    // State Contract Interface
    interface StateOperation {
        void execute(Payment payment);
    }

    // Centralize enum
    @Getter
    @AllArgsConstructor
    enum StrategyType {
        ACTIVE(new ActiveStateOperation()),
        PENDING(new PendingStateOperation()),
        INACTIVE(new InactiveStateOperation());

        final StateOperation stateOperation;
    }

    // Active State Impl
    static class ActiveStateOperation implements StateOperation {

        @Override
        public void execute(Payment payment) {
            // Subtract from balance
            payment.setAmount(payment.getAmount().subtract(BigDecimal.valueOf(100)));
            System.out.println("OPERATION = ACTIVE (minus 100) R:" + payment);
        }
    }

    // Pending State Impl
    static class PendingStateOperation implements StateOperation {

        @Override
        public void execute(Payment payment) {
            // Same balance remains
            System.out.println("OPERATION = PENDING (same) R:" + payment);
        }
    }

    // Inactive State Impl
    static class InactiveStateOperation implements StateOperation {

        @Override
        public void execute(Payment payment) {
            // add value to balance
            payment.setAmount(payment.getAmount().add(BigDecimal.valueOf(10)));
            System.out.println("OPERATION = INACTIVE (add 10) R:" + payment);
        }
    }

    // Business Object (BO)
    @Data
    @AllArgsConstructor
    static class Payment {

        private StrategyType type;
        private String name;
        private BigDecimal amount;

        // Visitor method
        public void processState() {
            type.getStateOperation().execute(this);
        }

    }

    // Example execution
    private static void run() {
        List<Payment> paymentList = List.of(
                new Payment(StrategyType.ACTIVE, "Payment 1", BigDecimal.valueOf(1_000)),
                new Payment(StrategyType.PENDING, "Payment 2", BigDecimal.valueOf(300)),
                new Payment(StrategyType.INACTIVE, "Payment 3", BigDecimal.valueOf(1_000_000))
        );
        for (Payment payment : paymentList) {
            payment.processState();
        }

    }

    public static void main(String[] args) {
        run();
    }

    /*
    Print OUTPUT from example:
    > Task :StatePattern.main()
        OPERATION = ACTIVE (minus 100) R:StatePattern.Payment(type=ACTIVE, name=Payment 1, amount=900)
        OPERATION = PENDING (same) R:StatePattern.Payment(type=PENDING, name=Payment 2, amount=300)
        OPERATION = INACTIVE (add 10) R:StatePattern.Payment(type=INACTIVE, name=Payment 3, amount=1000010)
     */

}