你可以用 ScriptEngineManager . 与 scriptEngine.eval(expression) 这个 expression 脚本将被执行。
然后你可以做：

List<Data> dataList = new ArrayList<>();
    dataList.add(new Data(2, 3));
    dataList.add(new Data(6, 2));
    ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
    ScriptEngine scriptEngine = scriptEngineManager.getEngineByName("JavaScript");
    dataList.forEach(data -> {
        try {
            System.out.println(scriptEngine.eval(data.getExpression("3*a+5*b")));
        } catch (ScriptException e) {
            e.printStackTrace();
        }
    });

与 Data 班级：

public class Data {
    int a, b;
    public Data(int a, int b) {
        this.a = a;
        this.b = b;
    }
    public String getExpression(String expression) {
        return expression.replaceAll("a", "" + a).replaceAll("b", "" + b);
    }
}