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SATURDAY, DECEMBER 8, 2012
How to reverse String in Java with or without StringBuffer
Example
Reverse String in Java
There are many ways to reverse String in Java. You can use rich Java API to quickly reverse contents of any String
object. Java library provides StringBuffer and StringBuilder class with reverse() method which can be
used to reverse String in Java. Since converting between String and StringBuffer or StringBuilder is very
easy it's the most easy way available to reverse String in Java. At the same time Writing Java program to reverse
String in Java without StringBuffer is one of the popular Java String interview question, which requires you to
reverse String by applying logic and by not using API methods. Since reverse is a recursive job, you can use
recursion as well as loop to reverse String in Java. In this Java tutorial I have shown How to reverse String using
StringBuffer, StringBuilder and using pure loop with logic. You can also check How to reverse String with
recursion in Java, if you want to see recursive code. let's see complete Java program for this beautiful Java
programming exercise.
Java program to reverse String in Java
Here is my complete code program to reverse any String in Java. In main method we have first
used StringBuffer andStringBuilder to reverse contents of String and then we wrote our own logic to reverse
String. This usestoCharArray() method of String class which return character array of String. By looping through
character array and appending it into empty String we can get reversed String in Java, as shown in following
example.
/**
*
* Java program to reverse String in Java. There are multiple ways to reverse
* String in Java, you can either take help of standard Java API StringBuffer
* to reverse String in Java. StringBuffer has a reverse() method which return
StringBuffer
* with reversed contents. On the other hand you can also reverse it by applying your
* own logic, if asked to reverse String without using StringBuffer in Java. By the
way
* you can also use StringBuilder to reverse String in Java. StringBuilder is non
thread-safe
* version of StringBuffer and provides similar API. You can use StringBuilder's
reverse()
* method to reverse content and then convert it back to String
*
* @author http://java67.blogspot.com
*/
public class StringReverseExample {
public static void main(String args[]) {

2. //quick wasy to reverse String in Java - Use StringBuffer
String word = "HelloWorld";
String reverse = new StringBuffer(word).reverse().toString();
System.out.printf(" original String : %s , reversed String %s %n", word,
reverse);
//another quick to reverse String in Java - use StringBuilder
word = "WakeUp";
reverse = new StringBuilder(word).reverse().toString();
System.out.printf(" original String : %s , reversed String %s %n", word,
reverse);
//one way to reverse String without using StringBuffer or StringBuilder is
writing
//own utility method
word = "Band";
reverse = reverse(word);
System.out.printf(" original String : %s , reversed String %s %n", word,
reverse);
}
public static String reverse(String source){
if(source == null || source.isEmpty()){
return source;
}
String reverse = "";
for(int i = source.length() -1; i>=0; i--){
reverse = reverse + source.charAt(i);
}
return reverse;
}
}
Output:
original String : HelloWorld , reversed String dlroWolleH
original String : WakeUp , reversed String pUekaW
original String : Band , reversed String dnaB
That's all on How to reverse String in Java with and without StringBuffer and StringBuilder. Though being a
Java programmer I prefer to use library and suggest any one to use StringBuffer or StringBuilder to reverse
String for any production use. Though its also a good programming exercise and you should practice it before going
for any Java programming interview.
Other Java tutorials you may like
String matches examples in Java
Difference between String and StringBuffer in Java
Best way to convert numbers to String in Java
Difference between == and equals method in Java
How to create Enum from String in Java
How to use contains and indexOf method in String Java
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4. [?]
Posted by Javin Paul at 3:04 AM
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Labels: coding, core java, core java interview question answer, programming
1 comment:
1.
RakeshJanuary 8, 2013 at 11:09 PM
Indeed it's commonly asked to write a Java program to reverse String in Java
without using reverse function and it's not EASY. first of all reverse can have
different meaning e.g. reverse word by word or reverse each character,
preserving whitespace etc. They may ask you to use recursion to write reverse
String function instead of using for loop. Best way is to prepare well with all
kinds of String related question.
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