In this article, we will discuss 10 ways to invert strings in Java, and invert strings through 10 Java programs. For example, invert the string "javaguides" to "sediugavaj".
1. Use the + (String connection) operator
package .string;
/**
*
* @author Ramesh Fadatare
*
*/
public class ReverseWithStringConcat {
public static void main(String[] args) {
ReverseWithStringConcat concat = new ReverseWithStringConcat();
("javaguides");
}
private String reverseWithStringConcat(String input) {
String output = new String();
for (int i = (() - 1); i >= 0; i--) {
output += ((i));
}
display(input, output);
return output;
}
private void display(String input, String output) {
(" input string :: " + input);
(" output string :: " + output);
}
}
Output:
input string :: javaguides
output string :: sediugavaj
2. Use StringBuilder
package ;
/**
*
* @author Ramesh Fadatare
*
*/
public class ReverseWithStringBuilderBuiltinMethod {
public static void main(String[] args) {
ReverseWithStringBuilderBuiltinMethod builtinMethod = new ReverseWithStringBuilderBuiltinMethod();
("javaguides");
}
public String reverseWithStringBuilderBuiltinMethod(String string) {
final StringBuilder builder = new StringBuilder(string);
display(string, ().toString());
return ().toString();
}
private void display(String input, String output) {
(" input string :: " + input);
(" output string :: " + output);
}
}
Output: RightJava technology, architecture technologyInterested students, welcome to joinQ Jun Sheep:625241190, learn together and discuss with each other.
input string :: javaguides
output string :: sediugavaj
3. Use the String charAt method
package ;
/**
*
* @author Ramesh Fadatare
*
*/
public class ReverseWithStringChatAt{
public static void main(String[] args) {
ReverseWithStringChatAt reverseWithStringBuilder = new ReverseWithStringChatAt();
("javaguides");
}
public String reverseWithStringChatAt(String string) {
final StringBuilder builder = new StringBuilder();
for (int i = (() - 1); i >= 0; i--) {
((i));
}
display(string, ());
return ();
}
private void display(String input, String output) {
(" input string :: " + input);
(" output string :: " + output);
}
}
Output:
input string :: javaguides
output string :: sediugavaj
4. Invert by exchanging characters
package ;
/**
*
* @author Ramesh Fadatare
*
*/
public class ReverseStringWithSwaps {
public static void main(String[] args) {
ReverseStringWithSwaps stringWithSwaps = new ReverseStringWithSwaps();
("javaguides");
}
public String reverseWithSwaps(String string) {
final char[] array = ();
final int length = - 1;
final int half = (int) ( / 2);
char c;
for (int i = length; i >= half; i--) {
c = array[length - i];
array[length - i] = array[i];
array[i] = c;
}
display(string, (array));
return (array);
}
private void display(String input, String output) {
(" input string :: " + input);
(" output string :: " + output);
}
}
Output:
input string :: javaguides
output string :: sediugavaj
5. Use the XOR(^) operator to invert
package ;
/**
*
* @author Ramesh Fadatare
*
*/
public class ReverseStringWithXOR {
public static void main(String[] args) {
ReverseStringWithXOR stringWithXOR = new ReverseStringWithXOR();
("javaguides");
}
public String reverseWithXOR(String string) {
final char[] array = ();
final int length = ;
final int half = (int) ( / 2);
for (int i = 0; i < half; i++) {
array[i] ^= array[length - i - 1];
array[length - i - 1] ^= array[i];
array[i] ^= array[length - i - 1];
}
display(string, (array));
return (array);
}
private void display(String input, String output) {
(" input string :: " + input);
(" output string :: " + output);
}
}
Output:
input string :: javaguides
output string :: sediugavaj
6. Use the stack
package ;
import ;
/**
*
* @author Ramesh Fadatare
*
*/
public class ReverseStringUsingStack {
// Function to reverse a string in Java using a stack and character array
public static String reverse(String str) {
// base case: if string is null or empty
if (str == null || (""))
return str;
// create an empty stack of characters
Stack < Character > stack = new Stack < Character > ();
// push every character of the given string into the stack
char[] ch = ();
for (int i = 0; i < (); i++)
(ch[i]);
// start from index 0
int k = 0;
// pop characters from the stack until it is empty
while (!()) {
// assign each popped character back to the character array
ch[k++] = ();
}
// convert the character array into string and return it
return (ch);
}
public static void main(String[] args) {
String str = "javaguides";
str = reverse(str); // string is immutable
("Reverse of the given string is : " + str);
}
}
Output:
Reverse of the given string is : sediugavaj
7. Use the Collections reverse() method
package ;
import ;
import ;
import ;
/**
*
* @author Ramesh Fadatare
*
*/
public class ReverseStringUsingCollectionsReverseMethod {
// Function to reverse a string in Java using ()
public static String reverse(String str) {
// base case: if string is null or empty
if (str == null || (""))
return str;
// create an empty list of characters
List < Character > list = new ArrayList < Character > ();
// push every character of the given string into it
for (char c: ())
(c);
// reverse list using reverse()
(list);
// covert ArrayList into String using StringBuilder and return it
StringBuilder builder = new StringBuilder(());
for (Character c: list)
(c);
return ();
}
public static void main(String[] args) {
String str = "Java Guides";
// String is immutable
str = reverse(str);
("Reverse of the given string is : " + str);
}
}
Output:
Reverse of the given string is : sediuG avaJ
8. Using Byte arrays
package ;
/**
*
* @author Ramesh Fadatare
*
*/
public class ReverseStringUsingByteArray {
// Function to reverse a string in Java using byte array
public static String reverse(String str) {
// return if string is null or empty
if (str == null || (""))
return str;
// convert string into bytes
byte[] bytes = ();
// start from the two end points l and h of the given string
// and increment l & decrement h at each iteration of the loop
// until two end-points intersect (l >= h)
for (int l = 0, h = () - 1; l < h; l++, h--) {
// Swap values at l and h
byte temp = bytes[l];
bytes[l] = bytes[h];
bytes[h] = temp;
}
// convert byte array back into the string
return new String(bytes);
}
public static void main(String[] args) {
String str = "Java Guides";
// String is immutable
str = reverse(str);
("Reverse of the given string is : " + str);
}
}
Output:
Reverse of the given string is : sediuG avaJ
9. Use substring() method
package ;
/**
*
* @author Ramesh Fadatare
*
*/
public class UsingSubStringFunction {
// Function to reverse a string in Java using recursion
private static String reverse(String str) {
// base case: if string is null or empty
if (str == null || (""))
return str;
// last character + recurse for remaining string
return (() - 1) + reverse((0, () - 1));
}
public static void main(String[] args) {
String str = "javaguides";
// string is immutable
str = reverse(str);
("Reverse of the given string is : " + str);
}
}
Output:
Reverse of the given string is : sediugavaj
10. Use Recursion
package ;
/**
*
* @author Ramesh Fadatare
*
*/
public class UsingRecursion {
static int i = 0;
// Recursive function to reverse a string in Java using static variable
private static void reverse(char[] str, int k) {
// if we have reached the end of the string
if (k == )
return;
// recurse for next character
reverse(str, k + 1);
if (i <= k) {
char temp = str[k];
str[k] = str[i];
str[i++] = temp;
}
}
public static String reverse(String str) {
// base case: if string is null or empty
if (str == null || (""))
return str;
// convert string into a character array
char[] A = ();
// reverse character array
reverse(A, 0);
// convert character array into the string
return (A);
}
public static void main(String[] args) {
String str = "Java Guides";
// string is immutable
str = reverse(str);
("Reverse of the given string is : " + str);
}
}
Output:
Reverse of the given string is : sediuG avaJ