public class BranchAndBoundExt extends BranchAndBound {
    private ExtNode node;

    public BranchAndBoundExt (int[] v, int n, int k, int c) {
        super();
        this.node = new ExtNode(v, n, k, c);
        node.calculateHeuristicValue();
        rootNode = this.vNode;
        branchAndBound(rootNode);
    }
}
----------------------------------------

public class ExtNode extends Node {
    static int n;
    static int[] v;
    static int k; // how many items we choose
    static int c; // the quantity we want
    static boolean[] mark; //whether you get or not an element
    static int sum; //cumulative sum in a state

public ExtNode(int[] v, int n, int k, int c) {
        super();
        NumberVector.n = n;
        NumberVector.k = k;
        NumberVector.c = c;
        NumberVector.v = v;

        mark = new boolean[n];
        sum = 0;
    }

 @Override
    public boolean isSolution() {
        return depth == k && sum == c;
    }