Java way to check if a string is palindrome

Question

I want to check if a string is a palindrome or not  I would like to learn an easy method to check the same using least possible string manipulations

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I m new to java and I m taking up your question as a challenge to improve my knowledge as well so please forgive me if this does not answer your question well   import java util ArrayList  import java util List   public class PalindromeRecursiveBoolean        public static boolean isPalindrome String str             str   str toUpperCase            char   strChars   str toCharArray             List lt Character gt  word   new ArrayList lt  gt             for  char c   strChars                word add c                      while  true                if   word size      1      word size      0                     return true                            if  word get 0     word get word size   - 1                     word remove 0                   word remove word size   - 1                 else                   return false                                       If the string is made of no letters or just one letter  it is a palindrome  Otherwise  compare the first and last letters of the string   If the first and last letters differ  then the string is not a palindrome Otherwise  the first and last letters are the same  Strip them from the string  and determine whether the string that remains is a palindrome  Take the answer for this smaller string and use it as the answer for the original string then repeat from 1     The only string manipulation is changing the string to uppercase so that you can enter something like  XScsX

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Using reverse is overkill because you don t need to generate an extra string  you just need to query the existing one   The following example checks the first and last characters are the same  and then walks further inside the string checking the results each time   It returns as soon as s is not a palindrome   The problem with the reverse approach is that it does all the work up front   It performs an expensive action on a string  then checks character by character until the strings are not equal and only then returns false if it is not a palindrome   If you are just comparing small strings all the time then this is fine  but if you want to defend yourself against bigger input then you should consider this algorithm   boolean isPalindrome String s      int n   s length      for  int i   0  i  lt   n 2     i         if  s charAt i     s charAt n - i - 1              return false                return true

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You can try something like this        String variable        write a string name      StringBuffer rev   new StringBuffer variable  reverse          String strRev   rev toString          if variable equalsIgnoreCase strRev     Check the condition

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check this condition  String string    some string        check this    if string equals  string reverse      it is palindrome

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Here is a simple one   public class Palindrome        public static void main String    args           Palindrome pn   new Palindrome             if pn isPalindrome  ABBA                 System out println  Palindrome              else               System out println  Not Palindrome                            public boolean isPalindrome String original           int i   original length  -1          int j 0          while i  gt  j                if original charAt i     original charAt j                     return false                            i--              j                      return true

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import java util Scanner   public class FindAllPalindromes   static String longestPalindrome  public String oldPalindrome     static int longest   public void allSubstrings String s               for int i 0 i lt s length   i             for int j 1 j lt  s length  -i j                 String subString s substring i  i j                 palindrome subString                                             public void palindrome String sub       System out println  String to b checked is   sub       StringBuilder sb new StringBuilder        sb append sub          append string to string builder      sb reverse                if sub equals sb toString                                palindrome condition          System out println  the given String    sub   is a palindrome            longestPalindrome sub             else          System out println  the string   sub  iss not a palindrome                    public void longestPalindrome String s               if s length   gt longest                            longest s length            longestPalindrome s             else if  s length    longest               oldPalindrome longestPalindrome          longestPalindrome s                public static void main String   args    FindAllPalindromes fp new FindAllPalindromes         Scanner sc new Scanner System in           System out println  Enter the String           String s sc nextLine         fp allSubstrings s             sc close        if fp oldPalindrome length   gt 0       System out println longestPalindrome  and  fp oldPalindrome   is the longest palindrome                else          System out println longestPalindrome   is the longest palindrome

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For the least lines of code and the simplest case  if s equals new StringBuilder s  reverse   toString        is a palindrome

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Here s a good class     public class Palindrome      public static boolean isPalindrome String stringToTest        String workingCopy   removeJunk stringToTest       String reversedCopy   reverse workingCopy        return reversedCopy equalsIgnoreCase workingCopy          protected static String removeJunk String string        int i  len   string length        StringBuffer dest   new StringBuffer len       char c       for  i    len - 1   i  gt   0  i--          c   string charAt i         if  Character isLetterOrDigit c             dest append c                      return dest toString           protected static String reverse String string        StringBuffer sb   new StringBuffer string        return sb reverse   toString           public static void main String   args        String string    Madam  I m Adam         System out println        System out println  Testing whether the following              string is a palindrome         System out println          string       System out println         if  isPalindrome string           System out println  It IS a palindrome           else         System out println  It is NOT a palindrome               System out println            Enjoy

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I guess this is simple way to check palindrome  String strToRevrse    MOM    strToRevrse equalsIgnoreCase new StringBuilder strToRevrse  reverse   toString

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public boolean isPalindrom String text        StringBuffer stringBuffer   new StringBuffer text        return stringBuffer reverse   toString   equals text

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public static boolean istPalindrom char   word   int i1   0  int i2   word length - 1  while  i2  gt  i1        if  word i1     word i2             return false              i1      --i2    return true

[java] Java way to check if a string is palindrome

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