483: Mainline

To make use of the strings produced by readLine, you first need to exploit several methods found in the String class:

• The trim method produces a string with no spaces or other whitespace characters on the ends. For example, if line = " 4 7 3 ", then:

  line.trim() --> "4 7 3" 
  

• The indexOf method finds the position of its ordinary argument in its target argument. If line = "4 7 3", then:

  line.indexOf(" ") --> 1 
  

• The substring method, with one indexing argument, extracts a string from its target argument, starting at the index.

  line.substring(2) --> "7 3" 
  

• The substring method, with two indexing arguments, extracts a string from its target argument.

  line".substring(0, 1) --> "4"