How can I fill a string with a character up to the exact length?-CodePudding

I have strings with different length, I want to fill them by symbol space, for example, to get string of the same length.

For instance, I have:

"1"
"3"
"12"

I need to get next result:

"  1"
"  3"
" 12"

Where all strings have length equals 3.

Additional question: Or maybe you know, how to initialize string of exact length that is filled one symbol. For example, String that has 5 space symbols.

" "

CodePudding user response：

You could use Scala API padTo to do what you need.

The only difference is that padTo appends elements but you need it to prepend. It's easy to do it with double reverse

def padLeft(string: String, size: Int, char: Char) = {
  string.reverse.padTo(size, char).reverse.mkString
}

Now, you can call it as following

padLeft("1", 3, ' ') .ensuring(_ == "  1")
padLeft("3", 3, ' ') .ensuring(_ == "  3")
padLeft("12", 3, ' ').ensuring(_ == " 12")

ensuring is added to assert that the value equals to the expected one.

If you want to create a string filled with the same element, you can do it via collections API. For example this way

val string = LazyList.fill(5)(' ').mkString
string.ensuring(_ == "     ")

CodePudding user response：

  def leftPad(str: String, length: Int, char: Char): String = {
    val diff = length - str.length
    if (diff <= 0) str
    else {
      val sb = new StringBuilder
      for (_ <- 0 until diff) sb.append(char)
      sb.append(str).toString()
    }
  }