优化以下代码：if (mode == 9) { if (modeId == PIEB_LOCK_TIME.getCode()) { return MultiLanguageUtil.message(TRUE_PIEB_LOCK_TIME.getLanguageKey(), locale); } else if (modeId == PIEB_RATE.getCode()) { return MultiLanguageUtil.message(TRUE_PIEB_RATE.getLanguageKey(), locale); } else if (modeId == PIEB_ONE_VTBI.getCode()) { return MultiLanguageUtil.message(TRUE_PIEB_ONE_VTBI.getLanguageKey(), locale); } else if (modeId == PIEB_LOAD_VTBI.getCode()){ return MultiLanguageUtil.message(TRUE_PIEB_LOAD_VTBI.getLanguageKey(), locale); } else if (modeId == PIEB_ONE_HOUR_MAX_VOLUME.getCode()){ return MultiLanguageUtil.message(TRUE_PIEB_ONE_HOUR_MAX_VOLUME.getLanguageKey(), locale); } else if (modeId == PIEB_FOUR_HOUR_MAX_VOLUME.getCode()){ return MultiLanguageUtil.message(TRUE_PIEB_FOUR_HOUR_MAX_VOLUME.getLanguageKey(), locale); } else { return MultiLanguageUtil.message(TRUE_CONTINUE_RATE.getLanguageKey(), locale); } }

以下是对给定代码的优化建议：

if (mode == 9) {
    if (modeId == PIEB_LOCK_TIME.getCode()) {
        return MultiLanguageUtil.message(TRUE_PIEB_LOCK_TIME.getLanguageKey(), locale);
    } else if (modeId == PIEB_RATE.getCode()) {
        return MultiLanguageUtil.message(TRUE_PIEB_RATE.getLanguageKey(), locale);
    } else if (modeId == PIEB_ONE_VTBI.getCode()) {
        return MultiLanguageUtil.message(TRUE_PIEB_ONE_VTBI.getLanguageKey(), locale);
    } else if (modeId == PIEB_LOAD_VTBI.getCode()){
        return MultiLanguageUtil.message(TRUE_PIEB_LOAD_VTBI.getLanguageKey(), locale);
    } else if (modeId == PIEB_ONE_HOUR_MAX_VOLUME.getCode()){
        return MultiLanguageUtil.message(TRUE_PIEB_ONE_HOUR_MAX_VOLUME.getLanguageKey(), locale);
    } else if (modeId == PIEB_FOUR_HOUR_MAX_VOLUME.getCode()){
        return MultiLanguageUtil.message(TRUE_PIEB_FOUR_HOUR_MAX_VOLUME.getLanguageKey(), locale);
    } else {
        return MultiLanguageUtil.message(TRUE_CONTINUE_RATE.getLanguageKey(), locale);
    }
}

可以使用`switch`语句来替代多个`if-else`语句，使代码更简洁和易读。优化后的代码如下：

if (mode == 9) {
    switch (modeId) {
        case PIEB_LOCK_TIME.getCode():
            return MultiLanguageUtil.message(TRUE_PIEB_LOCK_TIME.getLanguageKey(), locale);
        case PIEB_RATE.getCode():
            return MultiLanguageUtil.message(TRUE_PIEB_RATE.getLanguageKey(), locale);
        case PIEB_ONE_VTBI.getCode():
            return MultiLanguageUtil.message(TRUE_PIEB_ONE_VTBI.getLanguageKey(), locale);
        case PIEB_LOAD_VTBI.getCode():
            return MultiLanguageUtil.message(TRUE_PIEB_LOAD_VTBI.getLanguageKey(), locale);
        case PIEB_ONE_HOUR_MAX_VOLUME.getCode():
            return MultiLanguageUtil.message(TRUE_PIEB_ONE_HOUR_MAX_VOLUME.getLanguageKey(), locale);
        case PIEB_FOUR_HOUR_MAX_VOLUME.getCode():
            return MultiLanguageUtil.message(TRUE_PIEB_FOUR_HOUR_MAX_VOLUME.getLanguageKey(), locale);
    }
}
return MultiLanguageUtil.message(TRUE_CONTINUE_RATE.getLanguageKey(), locale);

通过使用`switch`语句，可以更清晰地表达逻辑，并减少代码的重复性。同时，提供了默认情况下的返回值。