如何为在一个循环中创建其所有JRadioButton的ButtonGroup设置setSelected？

我有以下for循环JRadioButton为ButtonGroup btgrpDiff我的每个值创建一个Difficulty enum：

private enum Difficulty {
    EASY("Easy"),
    MEDIUM("Medium"),
    HARD("Hard"),
    EXTRA_HARD("Extra Hard");

    public final String name;

    private Difficulty(String name) {
        this.name = name;
    }
}

for (Difficulty diff : Difficulty.values()) {
    JRadioButton radDiff = new JRadioButton(diff.name);
    radDiff.setActionCommand(diff.name);
    btgrpDiff.add(radDiff);
    panDiff.add(radDiff, "align 50%, shrink 2, wrap");
}

可我怎么setSelected对ButtonGroup btgrpDiff的外for循环？我想将它们全部选中后直接设置，或者为我的枚举中的每个难度级别设置一个布尔参数，以确定是否在for循环中将它们设置为选中状态，但是我不确定哪个会最好的，或者究竟如何获得ButtonModel的JRadioButton秒。