Java program to reverse a string

Java program to reverse a string:
In this page, you are going to learn how to reverse the string using various methods. The methods are char charAt(),int length(), char[] toCharArray(), byte[] getBytes(), StringBuffer append(). To reverse the words in a sentence String[] split() method is used.

Example 1:
// using the int length()  and charAt() method

import java.util.Scanner;
public class Example1
{
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
System.out.print("Enter the string: ");
String s = sc.nextLine();
System.out.println("Before reversing the string: " + s);
String reverse = "";
int n = s.length();
for(int i =n-1; i>=0; i--)
{
reverse = reverse + s.charAt(i);
}
System.out.println("After reversing a string: " + reverse);
}
}

Output:
Enter the string: Java Program
Before reversing the string: Java Program
After reversing a string: margorP avaJ

Example 2:
// using char[] toCharArray() method

import java.util.Scanner;
public class Example2
{
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
System.out.print("Enter the string: ");
String s = sc.nextLine();
System.out.println("Before reversing the string using toCharArray method: " + s);
String reverse = "";
char[] ch = s.toCharArray();
int n = ch.length;
for(int i=(n-1); i>=0;i--)
{
reverse = reverse + ch[i];
}
System.out.println("After reversing the string: " + reverse);
}
}

Output:
Enter the string: Java Program
Before reversing the string using toCharArray method: Java Program
After reversing the string: margorP avaJ

Example 3:

//using byte[] getBytes() method

import java.util.Scanner;

public class Example3

{

public static void main(String[] args)

{

Scanner sc = new Scanner(System.in);

System.out.print("Enter the string: ");

String s = sc.nextLine();

System.out.println("Before reversing the string using getBytes() method: " + s);

byte[] bt = s.getBytes();

char[] c = new char[bt.length];

for(int i=0;i<(bt.length);i++)

{

c[i] = (char)bt[(bt.length)-i-1];

}

System.out.println("After reversing the String: " + new String(c));

}

}

Output:

Enter the string: Java Program

Before reversing the string using getBytes() method: Java Program

After reversing the String: margorP avaJ

Example 4:

// using StringBuffer append() method

import java.util.Scanner;

public class Example4

{

public static void main(String[] args)

{

Scanner sc = new Scanner(System.in);

System.out.print("Enter the string: ");

String s = sc.nextLine();

System.out.println("Before reversing the string using StringBuffer append() method: " + s);

// you can either use StringBuilder append() method

StringBuffer sb = new StringBuffer();

for(int i=(s.length()-1);i>=0;i--)

{

sb.append(s.charAt(i));

}

System.out.println("After reversing the String: " + sb.toString());

}

}

Output:

Enter the string: Java Program

Before reversing the string using StringBuffer append() method: Java Program

After reversing the String: margorP avaJ

Example 5:

// Using String[] split() method - to reverse the words in a sentence.

import java.util.Scanner;

public class Example5

{

public static void main(String[] args)

{

Scanner sc = new Scanner(System.in);

System.out.print("Enter the sentence: ");

String s = sc.nextLine();

System.out.println("Before reversing using split() method: " + s);

String[] sp = s.split(" ");

StringBuffer sb = new StringBuffer();

for(int i = (sp.length - 1); i>=0;i--)

{

sb.append(sp[i]+" ");

}

System.out.println("After reversing: " + sb.toString());

}

}

Output:

Enter the sentence: This is a java program

Before reversing using split() method: This is a java program

After reversing: program java a is This

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