Create oneTwo.java

java/string-2/oneTwo.java

@@ -0,0 +1,24 @@
+/*
+ * Given a string, compute a new string by moving the first char to come after
+ * the next two chars, so "abc" yields "bca". Repeat this process for each
+ * subsequent group of 3 chars, so "abcdef" yields "bcaefd". Ignore any group of
+ * fewer than 3 chars at the end.
+ */
+public String oneTwo(String str) {
+  // creates a new string to append each reversed group of three to
+  String newString = "";
+  // for each whole group of three in the string
+  for (int i = 0; i < str.length() / 3; i++) {
+    // gets three letters by splitting the string starting at the index of the 
+    // group of three times three (because there are three charachters per group)
+    String threeLetters = str.substring(i * 3, i * 3 + 3);
+    // appends the first of the three letters to the end
+    threeLetters += threeLetters.charAt(0);
+    // appends the last three charachters of our new string (the original last two
+    // + the first original charachter) to the newstring
+    newString += threeLetters.substring(1, 4);
+  }
+  // returns our new string (with the reversed three letter group) + the remaining un-
+  // reversed charachters
+  return newString + newString.substring(newString.length() - (newString.length() % 3));
+}