Execute an Action in a Decision Tree

This example conditionally executes Java methods based on the outcome of executing a decision tree. It provides a flexible and programmable framework to define conditions and corresponding Java functions to be executed when those conditions are met in the decision tree.

For a detailed explanation of creating decision trees, see Evaluate a Decision Tree example where we also associate outcomes with certain conditions.

Real-life use cases for this library can be found in various domains where decision-making based on conditional logic is required. For example, in financial applications, the library can be used to automate loan approval processes. The decision tree can incorporate various factors such as credit score, income, and employment status, and based on these conditions, specific Java functions can be executed to either approve or reject the loan application.

Java Code Listing

package com.northconcepts.datapipeline.foundations.examples.decisiontree;

import com.northconcepts.datapipeline.core.Functions;
import com.northconcepts.datapipeline.core.Record;
import com.northconcepts.datapipeline.foundations.decisiontree.DecisionTree;
import com.northconcepts.datapipeline.foundations.decisiontree.DecisionTreeNode;
import com.northconcepts.datapipeline.foundations.decisiontree.DecisionTreeResult;
import com.northconcepts.datapipeline.internal.expression.DefaultExpressionContext;

public class ExecuteAnActionInADecisionTree {

    public static void action1() {
        System.out.println("Action 1");
    }

    public static double action2(int age, double income) {
        System.out.println("Age: " + age + ";  Income: " + income);
        return age * income;
    }

    public static void main(String[] args) {
        Functions.add("action2", "com.northconcepts.datapipeline.foundations.examples.decisiontree.ExecuteAnActionInADecisionTree.action2");

        DefaultExpressionContext input = new DefaultExpressionContext();
        input.setValue("Age", 49);
        input.setValue("houseOwned", true);
        input.setValue("Income", 1000.0);

        DecisionTree tree = new DecisionTree().setRootNode(new DecisionTreeNode()

            .addNode(new DecisionTreeNode("Age >= 40")

                .addNode(new DecisionTreeNode("houseOwned == true").addOutcome("Eligible", "true")
                    .addOutcome("Action1", "com.northconcepts.datapipeline.foundations.examples.decisiontree.ExecuteAnActionInADecisionTree.action1()")
                    .addOutcome("Action2", "action2(Age, Income)"))

                .addNode(new DecisionTreeNode("houseOwned == false")

                    .addNode(new DecisionTreeNode("Income >= 2000")
                        .addOutcome("Eligible", "true")
                        .addOutcome("Action1", "com.northconcepts.datapipeline.foundations.examples.decisiontree.ExecuteAnActionInADecisionTree.action1()")
                        .addOutcome("Action2", "action2(Age, Income)"))

                    .addNode(new DecisionTreeNode("Income < 2000")
                        .addOutcome("Eligible", "false")
                        .addOutcome("Action1", "com.northconcepts.datapipeline.foundations.examples.decisiontree.ExecuteAnActionInADecisionTree.action1()")
                        .addOutcome("Action2", "action2(Age, Income)"))))

            .addNode(new DecisionTreeNode("Age < 40")

                .addNode(new DecisionTreeNode("Income >= 3000")
                    .addOutcome("Eligible", "true")
                    .addOutcome("Action1", "com.northconcepts.datapipeline.foundations.examples.decisiontree.ExecuteAnActionInADecisionTree.action1()")
                    .addOutcome("Action2", "action2(Age, Income)"))

                .addNode(new DecisionTreeNode("Income < 3000")
                    .addOutcome("Eligible", "false")
                    .addOutcome("Action1", "com.northconcepts.datapipeline.foundations.examples.decisiontree.ExecuteAnActionInADecisionTree.action1()")
                    .addOutcome("Action2", "action2(Age, Income)"))));

        DecisionTreeResult result = tree.evaluate(input);
        Record outcome = result.getOutcome();

        System.out.println("outcome = " + outcome);
    }
}

Code Walkthrough

1. A DefaultExpressionContext is defined as the input of the decision tree where we set properties such as Age, houseOwned and Income.
2. Then, a DecisionTree is initialized with a root node and a variety of child nodes having conditions on properties Age, houseOwned and Income.
3. In order to attach an outcome with a node, addOutcome() method is invoked.
4. addOutcome() can also execute Java functions as actions; therefore some outcomes will invoke action1() and action2() methods respectively.
5. The input is then evaluated and stored in a DecisionTreeResult instance.
6. Finally, getOutcome() can be invoked to display the results of the evaluation on the console.

Console Output

Action 1
Age: 49;  Income: 1000.0
outcome = Record (MODIFIED) {
    0:[Eligible]:BOOLEAN=[true]:Boolean
    1:[Action1]:UNDEFINED=[null]
    2:[Action2]:DOUBLE=[49000.0]:Double
}