Recursion - Multimedia Introduction to Programming Using Java - page 397

Javanize and prepend . We coined the word javanize to mean “refine into Java”, or “replace by
an equivalent Java statement or expression”.
To append a value to a list means to insert it at the end of the list. There
exists no corresponding word to add the value at the beginning of the list, so we
have coined one. To prepend a value to a list means to insert it at the beginning
of the list.

15.1.3 A recursive function

We develop a function to return its String parameter but with blanks removed:

Activity
15-1.3

/** = p , with blank characters removed */
public static String deblank(String p)

For example, if the argument is the string " a b c " , the result of the call is the
string "abc" :

deblank(" a b c ") is "abc"

If the argument contains only blank characters (or no characters at all), the
result of the call is the empty String :

See lesson
page 15.1 to
get the function
from the CD.

deblank(" ") is ""

In writing the method body, there are two cases to consider. The base case is
the case that p is the empty String ; there are no blanks to remove, and p itself
can be returned.
The case that p contains at least one character itself breaks into two cases.
(1) If the first character of p is a blank, the result is the rest of p but with blanks
removed. (2) If the first character is not a blank, the result is the first character
prepended to (the rest of p but with blanks removed). This yields this body, with
some parts still in English:

if (p.length() == 0) {
return p;

}

// { p has at least one character }
if (p.charAt(0) == ' ')
{ r eturn p[1..] but with blanks removed ; }

// { first character of p is not a blank }
return p.charAt(0) + (p[1..] , but with blanks removed );

This function is correct, but it has two English expressions, which we have
to Javanize. The expression ( p[1..] but with blanks removed) is the same as the
value of the function given in the specification, except that the expression has
p[1..] instead of parameter p . Therefore, the expression can be implemented
using the Java expression