fall through:跳转
如:
switch(){
case 1:
break:
case 2:
fall through
break
case 3:
break
}
执行fall through时无视break继续往下执行
fall through:跳转
如:
switch(){
case 1:
break:
case 2:
fall through
break
case 3:
break
}
执行fall through时无视break继续往下执行