Question
Write a recursive method called writeChars that accepts an integer parameter n and that prints out a total of n characters. The middle character of the output should always be an asterisk ("*"). If you are asked to write out an even number of characters, then there will be two asterisks in the middle ("**"). Before the asterisk(s) you should write out less-than characters ("<"). After the asterisk(s) you should write out greater-than characters (">"). Your method should throw an IllegalArgumentException if it is passed a value less than 1. For example, the following calls produce the following output:
Method call Output produced
----------------------------------------
writeChars(1); *
writeChars(2); **
writeChars(3); <*>
writeChars(4); <**>
writeChars(5); <<*>>
writeChars(6); <<**>>
writeChars(7); <<<*>>>
writeChars(8); <<<**>>>
Answer
package recursion;
public class WriteCharacters {
public static void writeChars(int value) {
if (value < 1)
throw new IllegalArgumentException();
// hard assertions
if (value == 2) {
System.out.print(" * * ");
return;
}
// hard assertions
if (value == 1) {
System.out.print(" * ");
return;
}
System.out.print(" < ");
writeChars(value-2);
System.out.print(" > ");
}
public static void main(String[] args) {
// call the method
writeChars(9);
}
}
Output:
< < < < * > > > >