partner_project/src/generator/MiddleGenerator.java

package generator;

import util.ExpressionUtils;
import java.util.*;

public class MiddleGenerator implements ProblemGenerator {
    @Override
    public List<Problem> generateProblems(int count) {
        List<Problem> problems = new ArrayList<>();
        for (int i = 0; i < count; i++) {
            problems.add(ExpressionUtils.generateMiddleExpr());
        }
        return problems;
    }
}