From 9d9045f130e647ccc48f78c11a3b7980880c2a72 Mon Sep 17 00:00:00 2001
From: shouvikbhattacharya <shouvikbhattacharya@outlook.com>
Date: Thu, 8 Feb 2018 21:04:46 +0530
Subject: [PATCH] BAEL-1525: New changes added.

---
 .../java/com/baeldung/string/Palindrome.java  | 17 +++++++-
 .../string/WhenCheckingPalindrome.java        | 41 +++++++++++++++++++
 2 files changed, 56 insertions(+), 2 deletions(-)

diff --git a/core-java/src/main/java/com/baeldung/string/Palindrome.java b/core-java/src/main/java/com/baeldung/string/Palindrome.java
index 37284a5424..03b65d1a84 100644
--- a/core-java/src/main/java/com/baeldung/string/Palindrome.java
+++ b/core-java/src/main/java/com/baeldung/string/Palindrome.java
@@ -3,7 +3,8 @@ package com.baeldung.string;
 public class Palindrome {
 
     public boolean isPalindrome(String text) {
-        text = text.replaceAll("\\s+", "").toLowerCase();
+        text = text.replaceAll("\\s+", "")
+            .toLowerCase();
         int length = text.length();
         int forward = 0;
         int backward = length - 1;
@@ -19,7 +20,7 @@ public class Palindrome {
 
     public boolean isPalindromeReverseTheString(String text) {
         String reverse = "";
-        text = text.toLowerCase();
+        text = text.replaceAll("\\s+", "").toLowerCase();
         char[] plain = text.toCharArray();
         for (int i = plain.length - 1; i >= 0; i--)
             reverse += plain[i];
@@ -37,4 +38,16 @@ public class Palindrome {
         StringBuffer reverse = plain.reverse();
         return reverse.equals(plain);
     }
+
+    public boolean isPalindromeRecursive(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 true;
+    }
 }
diff --git a/core-java/src/test/java/com/baeldung/string/WhenCheckingPalindrome.java b/core-java/src/test/java/com/baeldung/string/WhenCheckingPalindrome.java
index eeaed09fff..e3655a3140 100644
--- a/core-java/src/test/java/com/baeldung/string/WhenCheckingPalindrome.java
+++ b/core-java/src/test/java/com/baeldung/string/WhenCheckingPalindrome.java
@@ -1,5 +1,7 @@
 package com.baeldung.string;
 
+import java.util.Arrays;
+
 import org.junit.Assert;
 import org.junit.Test;
 
@@ -68,6 +70,45 @@ public class WhenCheckingPalindrome {
     @Test
     public void whenStringBufferSentence_shouldBePalindrome() {
         for(String sentence:sentences)
+            
             Assert.assertTrue(palindrome.isPalindromeUsingStringBuffer(sentence));
     }
+    
+    @Test
+    public void whenPalindromeRecursive_wordShouldBePalindrome() {
+        for(String word:words) {
+            word = word.replaceAll("\\s+", "").toLowerCase();
+            int backward = word.length()-1;
+            
+            Assert.assertTrue(palindrome.isPalindromeRecursive(word,0,backward));
+        }
+    }
+    
+    @Test
+    public void whenPalindromeRecursive_sentenceShouldBePalindrome() {
+        for(String sentence:sentences) {
+            sentence = sentence.replaceAll("\\s+", "").toLowerCase();
+            int backward = sentence.length()-1;
+            
+            Assert.assertTrue(palindrome.isPalindromeRecursive(sentence,0,backward));
+        }
+    }
+    
+    @Test
+    public void whenPalindromeStreams_wordShouldBePalindrome() {
+        String[] expected = Arrays.stream(words)
+            .filter(palindrome::isPalindrome)
+            .toArray(String[]::new);
+        
+        Assert.assertArrayEquals(expected, words);
+    }
+    
+    @Test
+    public void whenPalindromeStreams_sentenceShouldBePalindrome() {
+        String[] expected = Arrays.stream(sentences)
+            .filter(palindrome::isPalindrome)
+            .toArray(String[]::new);
+        
+        Assert.assertArrayEquals(expected, sentences);
+    }
 }