whistle in the dark meaning in English

给自己壮胆

" whistle in the dark "
“在黑暗中吹口哨呢？ ”
He says that he is not afraid of losing his job , but i think he is just whistling in the dark
他说他不怕丢掉工作，可是我想他是在给自己虚张声势而已。
Jim said he could fight the bully with one hand , but we knew that he was whistling in the dark
吉姆说他一只手就可以对付这个暴徒，但我们知道他是在说大话壮胆子。
After the heavy snowfall the groundsman was whistling in the dark when he promised that the pitch would be clear for a three o ' clock kick - off
大雪之后，球场管理员答应3点钟足球比赛之前能把球场清理干净时，他实在是在强鼓勇气。