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| name: 'Comment on stale issues and PRs' | ||
| on: | ||
| schedule: | ||
| - cron: '30 1 * * *' | ||
|
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| jobs: | ||
| stale: | ||
| runs-on: ubuntu-latest | ||
| steps: | ||
| - uses: actions/stale@v9 | ||
| with: | ||
| stale-issue-message: 'This issue is stale because it has been open 60 days with no activity.' | ||
| stale-pr-message: 'This PR is stale because it has been open 60 days with no activity.' | ||
| close-issue-message: 'This issue was closed because it has been stalled for too long with no activity.' | ||
| close-pr-message: 'This PR was closed because it has been stalled for too long with no activity.' | ||
| days-before-issue-stale: 60 | ||
| days-before-pr-stale: 60 | ||
| days-before-issue-close: -1 | ||
| days-before-pr-close: -1 |
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| Original file line number | Diff line number | Diff line change |
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| --- | ||
| title: "Money Pattern in Java: Encapsulating Monetary Values with Currency Consistency" | ||
| shortTitle: Money | ||
| description: "Learn how the Money design pattern in Java ensures currency safety, precision handling, and maintainable financial operations. Explore examples, applicability, and benefits of the pattern." | ||
| category: Behavioral | ||
| language: en | ||
| tag: | ||
| - Encapsulation | ||
| - Precision handling | ||
| - Currency safety | ||
| - Value Object | ||
| - Financial operations | ||
| - Currency | ||
| - Financial | ||
| - Immutable | ||
| - Value Object | ||
| --- | ||
|
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| ## Also known as | ||
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| * Monetary Value Object | ||
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| ## Intent of Money Design Pattern | ||
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| The Money design pattern provides a robust way to encapsulate monetary values and their associated currencies. It ensures precise calculations, currency consistency, and maintainability of financial logic in Java applications. | ||
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| ## Detailed Explanation of Money Pattern with Real-World Examples | ||
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| ### Real-world example | ||
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| > Imagine an e-commerce platform where customers shop in their local currencies. The platform needs to calculate order totals, taxes, and discounts accurately while handling multiple currencies seamlessly. | ||
| In this example: | ||
| - Each monetary value (like a product price or tax amount) is encapsulated in a `Money` object. | ||
| - The `Money` class ensures that only values in the same currency are combined and supports safe currency conversion for global operations. | ||
|
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| ### In plain words | ||
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| > The Money pattern encapsulates both an amount and its currency, ensuring financial operations are precise, consistent, and maintainable. | ||
| ### Wikipedia says | ||
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| > "The Money design pattern encapsulates a monetary value and its currency, allowing for safe arithmetic operations and conversions while preserving accuracy and consistency in financial calculations." | ||
| ## Programmatic Example of Money Pattern in Java | ||
|
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| ### Money Class | ||
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| ```java | ||
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| /** | ||
| * Represents a monetary value with an associated currency. | ||
| * Provides operations for basic arithmetic (addition, subtraction, multiplication), | ||
| * as well as currency conversion while ensuring proper rounding. | ||
| */ | ||
| @Getter | ||
| public class Money { | ||
| private @Getter double amount; | ||
| private @Getter String currency; | ||
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| public Money(double amnt, String curr) { | ||
| this.amount = amnt; | ||
| this.currency = curr; | ||
| } | ||
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| private double roundToTwoDecimals(double value) { | ||
| return Math.round(value * 100.0) / 100.0; | ||
| } | ||
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| public void addMoney(Money moneyToBeAdded) throws CannotAddTwoCurrienciesException { | ||
| if (!moneyToBeAdded.getCurrency().equals(this.currency)) { | ||
| throw new CannotAddTwoCurrienciesException("You are trying to add two different currencies"); | ||
| } | ||
| this.amount = roundToTwoDecimals(this.amount + moneyToBeAdded.getAmount()); | ||
| } | ||
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| public void subtractMoney(Money moneyToBeSubtracted) throws CannotSubtractException { | ||
| if (!moneyToBeSubtracted.getCurrency().equals(this.currency)) { | ||
| throw new CannotSubtractException("You are trying to subtract two different currencies"); | ||
| } else if (moneyToBeSubtracted.getAmount() > this.amount) { | ||
| throw new CannotSubtractException("The amount you are trying to subtract is larger than the amount you have"); | ||
| } | ||
| this.amount = roundToTwoDecimals(this.amount - moneyToBeSubtracted.getAmount()); | ||
| } | ||
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| public void multiply(int factor) { | ||
| if (factor < 0) { | ||
| throw new IllegalArgumentException("Factor must be non-negative"); | ||
| } | ||
| this.amount = roundToTwoDecimals(this.amount * factor); | ||
| } | ||
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| public void exchangeCurrency(String currencyToChangeTo, double exchangeRate) { | ||
| if (exchangeRate < 0) { | ||
| throw new IllegalArgumentException("Exchange rate must be non-negative"); | ||
| } | ||
| this.amount = roundToTwoDecimals(this.amount * exchangeRate); | ||
| this.currency = currencyToChangeTo; | ||
| } | ||
| } | ||
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| ## When to Use the Money Pattern | ||
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| The Money pattern should be used in scenarios where: | ||
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| 1. **Currency-safe arithmetic operations** | ||
| To ensure that arithmetic operations like addition, subtraction, and multiplication are performed only between amounts in the same currency, preventing inconsistencies or errors in calculations. | ||
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| 2. **Accurate rounding for financial calculations** | ||
| Precise rounding to two decimal places is critical to maintain accuracy and consistency in financial systems. | ||
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| 3. **Consistent currency conversion** | ||
| When handling international transactions or displaying monetary values in different currencies, the Money pattern facilitates easy and reliable conversion using exchange rates. | ||
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| 4. **Encapsulation of monetary logic** | ||
| By encapsulating all monetary operations within a dedicated class, the Money pattern improves maintainability and reduces the likelihood of errors. | ||
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| 5. **Preventing errors in financial operations** | ||
| Strict validation ensures that operations like subtraction or multiplication are only performed when conditions are met, safeguarding against misuse or logical errors. | ||
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| 6. **Handling diverse scenarios in financial systems** | ||
| Useful in complex systems like e-commerce, banking, and payroll applications where precise and consistent monetary value handling is crucial. | ||
|
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| --- | ||
| ## Benefits and Trade-offs of Money Pattern | ||
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| ### Benefits | ||
| 1. **Precision and Accuracy** | ||
| The Money pattern ensures precise handling of monetary values, reducing the risk of rounding errors. | ||
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| 2. **Encapsulation of Business Logic** | ||
| By encapsulating monetary operations, the pattern enhances maintainability and reduces redundancy in financial systems. | ||
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| 3. **Currency Safety** | ||
| It ensures operations are performed only between amounts of the same currency, avoiding logical errors. | ||
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| 4. **Improved Readability** | ||
| By abstracting monetary logic into a dedicated class, the code becomes easier to read and maintain. | ||
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| 5. **Ease of Extension** | ||
| Adding new operations, handling different currencies, or incorporating additional business rules is straightforward. | ||
|
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| ### Trade-offs | ||
| 1. **Increased Complexity** | ||
| Introducing a dedicated `Money` class can add some overhead, especially for small or simple projects. | ||
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| 2. **Potential for Misuse** | ||
| Without proper validation and handling, incorrect usage of the Money pattern may introduce subtle bugs. | ||
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| 3. **Performance Overhead** | ||
| Precision and encapsulation might slightly affect performance in systems with extremely high transaction volumes. | ||
|
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| --- | ||
|
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| ## Related Design Patterns | ||
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| 1. **Value Object** | ||
| Money is a classic example of the Value Object pattern, where objects are immutable and define equality based on their value. | ||
| Link:https://martinfowler.com/bliki/ValueObject.html | ||
| 2. **Factory Method** | ||
| Factories can be employed to handle creation logic, such as applying default exchange rates or rounding rules. | ||
| Link:https://www.geeksforgeeks.org/factory-method-for-designing-pattern/ | ||
| --- | ||
|
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| ## References and Credits | ||
|
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| - [Patterns of Enterprise Application Architecture](https://martinfowler.com/eaaCatalog/money.html) by Martin Fowler | ||
| - [Design Patterns: Elements of Reusable Object-Oriented Software](https://amzn.to/3w0pvKI) |
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| <?xml version="1.0" encoding="UTF-8"?> | ||
| <!-- | ||
| This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt). | ||
| The MIT License | ||
| Copyright © 2014-2022 Ilkka Seppälä | ||
| Permission is hereby granted, free of charge, to any person obtaining a copy | ||
| of this software and associated documentation files (the "Software"), to deal | ||
| in the Software without restriction, including without limitation the rights | ||
| to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | ||
| copies of the Software, and to permit persons to whom the Software is | ||
| furnished to do so, subject to the following conditions: | ||
| The above copyright notice and this permission notice shall be included in | ||
| all copies or substantial portions of the Software. | ||
| THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
| IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | ||
| FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | ||
| AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | ||
| LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | ||
| OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | ||
| THE SOFTWARE. | ||
| --> | ||
| <project xmlns="http://maven.apache.org/POM/4.0.0" | ||
| xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" | ||
| xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> | ||
| <modelVersion>4.0.0</modelVersion> | ||
| <parent> | ||
| <groupId>com.iluwatar</groupId> | ||
| <artifactId>java-design-patterns</artifactId> | ||
| <version>1.26.0-SNAPSHOT</version> | ||
| </parent> | ||
|
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| <artifactId>money</artifactId> | ||
|
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| <dependencies> | ||
| <dependency> | ||
| <groupId>org.junit.jupiter</groupId> | ||
| <artifactId>junit-jupiter-api</artifactId> | ||
| <scope>test</scope> | ||
| </dependency> | ||
| </dependencies> | ||
|
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| </project> |
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