issue #66 Add Kata Diamond

src/main/java/com/ordestiny/tdd/kata/Diamond.java

@@ -0,0 +1,42 @@
+package com.ordestiny.tdd.kata;
+
+import java.util.Arrays;
+
+public class Diamond {
+
+ public final static char BASE_CHARACTER = 'A';
+
+ private Diamond() {
+
+ }
+
+ /**
+ * Build a string that represents a diamond based on a given character which is the widest point character in the
+ * constructed diamond.
+ *
+ * @param widestPointChar
+ * The character that is used to construct the widest points (diagonal) in th diamond.
+ * @return Constructed diamond string based on the given widest point character.
+ * @throws IllegalArgumentException
+ * If the argument provided as the widest point character is out of the A-Z range.
+ * @implNote For sake of simplicity, spaces and new lines are not included in the Diamond
+ * string.
+ */
+ public static String buildDiamond(char widestPointChar) throws IllegalArgumentException {
+ if (!Character.isUpperCase(widestPointChar)) {
+ throw new IllegalArgumentException("Supplied widest point character is not valid. Only A-Z is accepted.");
+ }
+
+ StringBuilder leftPart = new StringBuilder();
+ int offset = widestPointChar - BASE_CHARACTER;
+ for (int i = 0; i < offset; i++) {
+ for (int j = 0; j < i + 1; j++) {
+ leftPart.append((char) (BASE_CHARACTER + i));
+ }
+ }
+ char[] diagonalString = new char[offset + 1];
+ Arrays.fill(diagonalString, widestPointChar);
+ StringBuilder rightPart = new StringBuilder(leftPart).reverse();
+ return leftPart + String.valueOf(diagonalString) + rightPart;
+ }
+}

src/test/java/com/ordestiny/tdd/kata/DiamondTest.java

@@ -0,0 +1,54 @@
+package com.ordestiny.tdd.kata;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+public class DiamondTest {
+
+ @Test
+ public void buildDiamond_whenWidestPointCharIsNull_returnException() {
+ assertThrows(IllegalArgumentException.class, () -> Diamond.buildDiamond('1'));
+ }
+
+ @Test
+ public void buildDiamond_validWidestPointChars_returnCorrectDiamondString() {
+ Map<Character, String> diamonds = new HashMap<>();
+ diamonds.put('A', "A");
+ diamonds.put('B', "ABBA");
+ diamonds.put('C', "ABBCCCBBA");
+ diamonds.put('D', "ABBCCCDDDDCCCBBA");
+ diamonds.put('E', "ABBCCCDDDDEEEEEDDDDCCCBBA");
+ diamonds.forEach(this::verifyDiamondString);
+ }
+
+ private void verifyDiamondString(char widestPointChar, String diamond) {
+ assertEquals(Diamond.buildDiamond(widestPointChar), diamond);
+ }
+
+ @Test
+ public void buildDiamond_widestPointCharSetToCharGreaterThanA_returnedValueHasCorrectNumberOfRepetitions() {
+ // In each generated diamond string, the widest point character is repeated one time more than its distance to
+ // the base character
+ for (char widestPointChar = 'B'; widestPointChar <= 'Z'; widestPointChar++) {
+ //assume
+ int diagonalLength = widestPointChar - Diamond.BASE_CHARACTER + 1;
+
+ //act
+ String diamondString = Diamond.buildDiamond(widestPointChar);
+
+ //assert
+ char[] diagonal = new char[diagonalLength];
+ Arrays.fill(diagonal, widestPointChar);
+
+ assertTrue(diamondString.contains(String.valueOf(diagonal)));
+ assertEquals(Math.pow(diagonalLength, 2), diamondString.length());
+ }
+ }
+
+}