How do I make object to update its value, based on other objects value change, in Java?

Question

I'm trying to make basic neural.network simulation. It consists of Neurons and NeuronConnections. In code below, the value of neuron2, should change whenever value of neuron1 is updated:

public class Main {

    public static void main(String[] args) {
        Neuron neuron1 = new Neuron();
        Neuron neuron2 = new Neuron();

        NeuronConnection neuronConnection = new NeuronConnection(neuron1, neuron2);

        neuron1.addInput(20);
        System.out.println(neuron2.getOutput());
    }
}

For now, I get just "0" which is default value.

Here is code for Neuron and NeuronConncetion objects:

public class Neuron {
    private double output;
    private List<Double> inputArray;

    public Neuron() {
        output = 0;
        inputArray = new LinkedList<>();
    }

    public Neuron (double input) {
        inputArray = new LinkedList<>();
        inputArray.add(input);
        output += input;
    }

    public void addInput(double input) {
        inputArray.add(input);
        output += input;
    }

    public void addMultipleInputs(List<Double> inputs) {
        inputArray.addAll(inputs);
        for (double input: inputs) {
            output += input;
        }
    }

    public double getOutput() {
        return output;
    }
}

public class NeuronConnection {
    private double weight;
    private Neuron inNeuron;
    private Neuron outNeuron;
    private double outValue;

    public NeuronConnection(Neuron inNeuron, Neuron outNeuron) {
        this.inNeuron = inNeuron;
        this.outNeuron = outNeuron;
        weight = Math.random();
        outValue = inNeuron.getOutput()*weight;
        outNeuron.addInput(outValue);
    }

    public double getOutValue() {
        return outValue;
    }
}

The questions is : How do I make neuron2 change its value, whenever I change input of neuron1?

Answer 1

I am providing you a simple solution. You just have to keep a reference to NeuronConnection in Neuron class and add a method setConnection() and call NeuronConnection's update() method (which we'll add later in NeuronConnection ) from addInput() or addMultipleInputs() method of Neuron class . The new design of Neuron class:

public class Neuron {
    private NeuronConnection conn;
    private double output;
    private List<Double> inputArray;

    public Neuron() {
        output = 0;
        inputArray = new LinkedList<>();
    }

    public Neuron (double input) {
        inputArray = new LinkedList<>();
        inputArray.add(input);
        output += input;
    }

    public void addInput(double input) {
        inputArray.add(input);
        output += input;
        conn.update();
    }

    public void addMultipleInputs(List<Double> inputs) {
        inputArray.addAll(inputs);
        for (double input: inputs) {
            output += input;
        }
        conn.update();
    }

    public double getOutput() {
        return output;
    }

    // i've added this method
    public void setConnection(NeuronConnection conn) {
        this.conn = conn;
    }
}

Now, redesign your NeuronConnection class:

public class NeuronConnection {
    private double weight;
    private Neuron inNeuron;
    private Neuron outNeuron;
    private double outValue;

    public NeuronConnection(Neuron inNeuron, Neuron outNeuron) {
        this.inNeuron = inNeuron;
        this.outNeuron = outNeuron;

        // now, setConnection
        this.inNeuron.setConnection(this);
        this.outNeuron.setConnection(this);

        weight = Math.random();
        outValue = inNeuron.getOutput()*weight;
        outNeuron.addInput(outValue);
    }

    public double getOutValue() {
        return outValue;
    }

    // i've added this
    public void update() {
      // this calculation is little flawed
      // you've to edit/fix this as you think it will be
      // perfect for your neural network
      outValue = inNeuron.getOutput() * weight;
      outNeuron.addInput(outValue);
    }
}

Now, the Main class, there's no change...

public class Main {

    public static void main(String[] args) {
        Neuron neuron1 = new Neuron();
        Neuron neuron2 = new Neuron();

        NeuronConnection neuronConnection = new NeuronConnection(neuron1, neuron2);

        neuron1.addInput(20);
        System.out.println(neuron2.getOutput());
    }
}

I haven't tested the code, but it should get you on the right track...

Let me know, if you've any question...