What are @ParameterType and custom Cucumber Expressions?

// Step text: When the user selects "ADMIN" role
@When("the user selects {string} role")
public void selectRole(String roleString) {
    Role role = Role.valueOf(roleString);  // manual conversion everywhere
    userPage.selectRole(role);
}

import io.cucumber.java.ParameterType;

public class CustomTypes {

    // Define custom type {role} that maps string → enum
    @ParameterType("ADMIN|MANAGER|USER|GUEST")
    public Role role(String roleString) {
        return Role.valueOf(roleString);
    }

    // Custom type for date
    @ParameterType("\\d{4}-\\d{2}-\\d{2}")
    public LocalDate date(String dateString) {
        return LocalDate.parse(dateString);
    }

    // Custom type for money
    @ParameterType("\\$\\d+\\.?\\d*")
    public BigDecimal amount(String amountString) {
        return new BigDecimal(amountString.replace("$", ""));
    }
}

Scenario: Admin creates new user
  When the admin assigns the ADMIN role to the new user
  Then the user should have ADMIN permissions

Scenario: Filter transactions by date
  When the user filters transactions from 2024-01-01 to 2024-12-31
  Then all transactions in that period should appear

Scenario: Apply discount
  When the user applies a discount of $15.00
  Then the cart total should reduce by $15.00

// Now uses {role} instead of {string}
@When("the admin assigns the {role} role to the new user")
public void assignRole(Role role) {
    // role is already a Role enum — no conversion needed
    adminPage.assignRole(role);
}

@When("the user filters transactions from {date} to {date}")
public void filterByDate(LocalDate from, LocalDate to) {
    // Already LocalDate objects — no parsing needed
    reportPage.setDateRange(from, to);
}

@When("the user applies a discount of {amount}")
public void applyDiscount(BigDecimal amount) {
    cartPage.applyDiscount(amount);
}

{string}    → "quoted text" → String
{int}       → 42           → Integer
{float}     → 3.14         → Float / Double
{word}      → singleword   → String
{bigdecimal}→ 9.99         → BigDecimal
{long}      → 123456789    → Long
{}          → anything     → String (anonymous)

// Cucumber Expression (simpler, recommended)
@When("the user enters {string} into the {word} field")

// Regex (more powerful, harder to read)
@When("^the user enters \"([^\"]*)\" into the (\\w+) field$")