// Create variables
GRBVar x = model.addVar(0.0, 1.0, 0.0, GRB.BINARY, "x");

// Set objective: maximize log(p) * x
GRBLinExpr expr = new GRBLinExpr();

for(Map.Entry<String, Double[]> entry: probabilityLevels.entrySet()) {

    Double[] probs = entry.getValue();

    for (Double prob: probs) {
        expr.addTerm(Math.log(prob), x);
    }
}

model.setObjective(expr, GRB.MAXIMIZE);