The Model interface wraps everything you define to build a simulation. Get started by learning how to build the credit card model.
\nFirst, create a new Java class in the same directory as Main.java in which you will implement the Model interface. In order to do so, right click on the directory and select new then Java File.
Insert implements Model after the class name and hit enter to automatically add the interface declaration at the top of the code.
CreditCard.java
\nimport simudyne.core.Model;\n\npublic class CreditCard implements Model {\n}The step() method is called at each tick of the model. The calculations for every tick are specified inside the step() method.
Start by creating a variable called balance set to 400 and incremented by 20% at every tick.
Overriding step CreditCard.java
\n import simudyne.core.Model;\n import simudyne.core.annotations.Variable;\n\n public class CreditCard implements Model {\n @Variable(name = \"Balance\")\n public float balance = 400;\n\n @Override\n public void step() {\n balance \\*= 1.2;\n }\n }Before running the model, add it to the Main.java class to register on the Server.
Registering a model Main.java
\n import simudyne.nexus.Server;\n import org.example.models.CreditCard.CreditCard;\n\n public class Main {\n public static void main(String[] args) {\n Server.register(\"My Credit Card\", CreditCard.class);\n Server.run();\n }\n }or run using the command:
\n$ Run Main\n$ simudyne-maven-java> mvn clean compile exec:java -Dexec.mainClass="Main" -s settings.xmlBy default, the console can be found at localhost:8080.
\nAfter launching the console, you will be brought to a list of models registered with the server. We have only registered \"My Credit Card\" so we only have one. Click on the model to be brought to the console for that model. Then, click the initialise button to initialise an interactive run.
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This will then display a number of buttons.
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\n Specify the macroStep In the console you will find inputs that you can control during the simulation. Your model class should look like this: CreditCard.java If you have followed our guidelines, your model output should closely resemble the following. \n @ModelSettings(timeUnit = \"MONTHS\", macroStep = 12)\npublic class CreditCard implements Model {}5. Final Model
\nimport simudyne.core.Model;\nimport simudyne.core.annotations.Input;\nimport simudyne.core.annotations.Variable;\n\n@ModelSettings(timeUnit = \"MONTHS\", macroStep = 12)\npublic class CreditCard implements Model {\n\n @Input(name = \"Spending\")\n public boolean isSpending = true;\n\n @Input(name = \"Spending Amount\")\n public float spending = 250f;\n\n @Input(name = \"Repayment Amount\")\n public float repayment = 200f;\n\n @Input(name = \"Interest Rate\")\n public float interest = 0.03f;\n\n @Variable(name = \"Balance\", initializable = true)\n public long balance = 400;\n\n @Variable(name = \"Interest Charge\")\n public float interest_charge() { return interest * balance; }\n\n @Variable(name = \"Balance Additions\")\n public float balance_additions() {\n return interest_charge() + (isSpending ? spending : 0);\n }\n\n // Model Interface Methods\n @Override\n public void step() {\n balance += balance_additions() - repayment;\n\n if (balance < 0) {\n balance = 0;\n }\n }\n}