BAEL-1525: Review comments incorporated. (#3639)

core-java/src/main/java/com/baeldung/string/Palindrome.java

@@ -5,49 +5,54 @@ import java.util.stream.IntStream;
 public class Palindrome {
 
     public boolean isPalindrome(String text) {
-        text = text.replaceAll("\\s+", "")
+        String clean = text.replaceAll("\\s+", "").toLowerCase();
-            .toLowerCase();
+        int length = clean.length();
-        int length = text.length();
         int forward = 0;
         int backward = length - 1;
-        boolean palindrome = true;
         while (backward > forward) {
-            char forwardChar = text.charAt(forward++);
+            char forwardChar = clean.charAt(forward++);
-            char backwardChar = text.charAt(backward--);
+            char backwardChar = clean.charAt(backward--);
             if (forwardChar != backwardChar)
                 return false;
         }
-        return palindrome;
+        return true;
     }
 
     public boolean isPalindromeReverseTheString(String text) {
-        String reverse = "";
+        StringBuilder reverse = new StringBuilder();
-        text = text.replaceAll("\\s+", "").toLowerCase();
+        String clean = text.replaceAll("\\s+", "").toLowerCase();
-        char[] plain = text.toCharArray();
+        char[] plain = clean.toCharArray();
         for (int i = plain.length - 1; i >= 0; i--)
-            reverse += plain[i];
+            reverse.append(plain[i]);
-        return reverse.equals(text);
+        return (reverse.toString()).equals(clean);
     }
 
     public boolean isPalindromeUsingStringBuilder(String text) {
-        StringBuilder plain = new StringBuilder(text);
+        String clean = text.replaceAll("\\s+", "").toLowerCase();
+        StringBuilder plain = new StringBuilder(clean);
         StringBuilder reverse = plain.reverse();
-        return reverse.equals(plain);
+        return (reverse.toString()).equals(clean);
     }
 
     public boolean isPalindromeUsingStringBuffer(String text) {
-        StringBuffer plain = new StringBuffer(text);
+        String clean = text.replaceAll("\\s+", "").toLowerCase();
+        StringBuffer plain = new StringBuffer(clean);
         StringBuffer reverse = plain.reverse();
-        return reverse.equals(plain);
+        return (reverse.toString()).equals(clean);
     }
 
-    public boolean isPalindromeRecursive(String text, int forward, int backward) {
+    public boolean isPalindromeRecursive(String text) {
+        String clean = text.replaceAll("\\s+", "").toLowerCase();
+        return recursivePalindrome(clean, 0, clean.length() - 1);
+    }
+
+    private boolean recursivePalindrome(String text, int forward, int backward) {
         if (forward == backward)
             return true;
         if ((text.charAt(forward)) != (text.charAt(backward)))
             return false;
         if (forward < backward + 1) {
-            return isPalindromeRecursive(text, forward + 1, backward - 1);
+            return recursivePalindrome(text, forward + 1, backward - 1);
         }
 
         return true;
@@ -58,5 +63,4 @@ public class Palindrome {
         return IntStream.range(0, temp.length() / 2)
             .noneMatch(i -> temp.charAt(i) != temp.charAt(temp.length() - i - 1));
     }
-    
 }

core-java/src/test/java/com/baeldung/string/PalindromeTest.java

@@ -25,84 +25,73 @@ public class PalindromeTest {
     
     @Test
     public void whenWord_shouldBePalindrome() {
-        for(String word:words)
+        for (String word : words)
             assertTrue(palindrome.isPalindrome(word));
     }
 
     @Test
     public void whenSentence_shouldBePalindrome() {
-        for(String sentence:sentences)
+        for (String sentence : sentences)
             assertTrue(palindrome.isPalindrome(sentence));
     }
 
     @Test
     public void whenReverseWord_shouldBePalindrome() {
-        for(String word:words)
+        for (String word : words)
             assertTrue(palindrome.isPalindromeReverseTheString(word));
     }
 
     @Test
     public void whenReverseSentence_shouldBePalindrome() {
-        for(String sentence:sentences)
+        for (String sentence : sentences)
             assertTrue(palindrome.isPalindromeReverseTheString(sentence));
     }
 
     @Test
     public void whenStringBuilderWord_shouldBePalindrome() {
-        for(String word:words)
+        for (String word : words)
             assertTrue(palindrome.isPalindromeUsingStringBuilder(word));
     }
 
     @Test
     public void whenStringBuilderSentence_shouldBePalindrome() {
-        for(String sentence:sentences)
+        for (String sentence : sentences)
             assertTrue(palindrome.isPalindromeUsingStringBuilder(sentence));
     }
 
     @Test
     public void whenStringBufferWord_shouldBePalindrome() {
-        for(String word:words)
+        for (String word : words)
             assertTrue(palindrome.isPalindromeUsingStringBuffer(word));
     }
 
     @Test
     public void whenStringBufferSentence_shouldBePalindrome() {
-        for(String sentence:sentences)
+        for (String sentence : sentences)
-            
             assertTrue(palindrome.isPalindromeUsingStringBuffer(sentence));
     }
 
     @Test
     public void whenPalindromeRecursive_wordShouldBePalindrome() {
-        for(String word:words) {
+        for (String word : words)
-            word = word.replaceAll("\\s+", "").toLowerCase();
+            assertTrue(palindrome.isPalindromeRecursive(word));
-            int backward = word.length()-1;
-            
-            assertTrue(palindrome.isPalindromeRecursive(word,0,backward));
-        }
     }
 
     @Test
     public void whenPalindromeRecursive_sentenceShouldBePalindrome() {
-        for(String sentence:sentences) {
+        for (String sentence : sentences)
-            sentence = sentence.replaceAll("\\s+", "").toLowerCase();
+            assertTrue(palindrome.isPalindromeRecursive(sentence));
-            int backward = sentence.length()-1;
-            
-            assertTrue(palindrome.isPalindromeRecursive(sentence,0,backward));
-        }
     }
 
     @Test
     public void whenPalindromeStreams_wordShouldBePalindrome() {
-        for(String word:words) {
+        for (String word : words)
             assertTrue(palindrome.isPalindromeUsingIntStream(word));
     }
-    }
 
     @Test
     public void whenPalindromeStreams_sentenceShouldBePalindrome() {
-        for(String sentence:sentences) {
+        for (String sentence : sentences)
             assertTrue(palindrome.isPalindromeUsingIntStream(sentence));
     }
-    }
 }