I've different classes of items. Each item has `value` and `weight`. 

For example:

`ClassA: [A1, A2, A3]`

`ClassB: [B1, B2, B3]`

`ClassC: [C1, C2, C3]`

How should I modify classic 0-1 Knapsack problem so that algorithm optimize solution maximizing overall value, consider all items in class but allowed to pick at at most one item from one class?

```
package knapsack;

import java.util.ArrayList;
import java.util.List;

public class Knapsack {

    private int totalNumberOfItems;
    private int maxmimumKnapsackCapacityUnits;

    private double[][] optimum;
    private boolean[][] solution;

    private double [] value;
    private int [] weight;

    public Knapsack(int knapsackCapacityUnits, List<KnapsackItem> items){

        this.totalNumberOfItems = items.size();
        this.maxmimumKnapsackCapacityUnits = knapsackCapacityUnits;

        this.optimum = new double[items.size() + 1][knapsackCapacityUnits + 1];
        this.solution = new boolean[items.size() + 1][knapsackCapacityUnits + 1];

        this.value = new double[items.size() + 1];
        this.weight = new int[items.size() + 1];

        int index=1;
        for(KnapsackItem item : items){
            value[index] = item.value;
            weight[index] = item.weight;
            index++;
        }

}

public List<KnapsackItem> optimize(){

    for(int currentItem = 1; currentItem <= totalNumberOfItems; currentItem++){
        for(int currentWeightUnit = 1; currentWeightUnit <= maxmimumKnapsackCapacityUnits; currentWeightUnit++){

            double option1 = optimum[currentItem - 1][currentWeightUnit];

            double option2 = Integer.MIN_VALUE;

            if(weight[currentItem] <= currentWeightUnit){
                option2 = value[currentItem] + optimum[currentItem-1][currentWeightUnit - weight[currentItem]];
            }

            optimum[currentItem][currentWeightUnit] = Math.max(option1, option2);
            solution[currentItem][currentWeightUnit] = (option2 > option1);
        }
    }

    boolean take [] = new boolean[totalNumberOfItems + 1];
    for(int currentItem = totalNumberOfItems,
            currentWeightUnit = maxmimumKnapsackCapacityUnits; 
            currentItem > 0; currentItem --){
        if(solution[currentItem][currentWeightUnit]){
            take[currentItem] = true;
            currentWeightUnit = currentWeightUnit - weight[currentItem];
        }
        else{
            take[currentItem] = false;
        }
    }

    List<KnapsackItem> items = new ArrayList<KnapsackItem>();
    for(int i = 0; i < take.length; i++){
        KnapsackItem newItem = new KnapsackItem();
        newItem.value = value[i];
        newItem.weight = weight[i];
        newItem.isTaken = take[i];
        items.add(newItem);
    }

    return items;
}
}

```

Thanks!