I want to replace multiple spaces by a single space. I am using tr to do this. But it is also replacing new line with a space. How can I avoid it?

Code:

tr -s [:space:] ' '

Input:

He  llo

Wor  ld

how  are  you

Required Output:

He llo

Wor ld

how are you

My Output:

He llo Wor ld how are you