How to insert a string in beginning of another string in java?

Get the both strings, suppose we have a string str1 and the string to be added at begin of str1 is str2.
Get the both strings, suppose we have a string str1 and the string to be added at begin of str1 is str2.
Create a character array with the sum of lengths of the two Strings as its length.
Create a character array with the sum of lengths of the two Strings as its length.
Starting from 0th position fill each element in the array with the characters of str2.
Starting from 0th position fill each element in the array with the characters of str2.
Now, from (length of str2)th position to the end of the array fill the character from the 1st array.
Now, from (length of str2)th position to the end of the array fill the character from the 1st array.
import java.util.Scanner;
public class StringBufferExample {
   public static void main(String args[]) {
      System.out.println("Enter string1: ");
      Scanner sc= new Scanner(System.in);
      String str1 = sc.next();
      System.out.println("Enter string2: ");
      String str2 = sc.next();
      char charArray[] = new char[str1.length()+str2.length()];
      for(int i = 0; i < str2.length(); i++) {
         charArray[i]= str2.charAt(i);
      }
      for(int i = str2.length(); i < charArray.length; i++ ) {
         charArray[i] = str1.charAt(i-str2.length());
      }
      String result = new String(charArray);
      System.out.println(result);
   }
}
Enter string1:
krishna
Enter string2:
kasyap
kasyapkrishna
Java provides StringBuffer class as a replacement of Strings in places where there is a necessity to make a lot of modifications to Strings of characters. You can modify/manipulate the contents of a StringBuffer over and over again without leaving behind a lot of new unused objects.
The append() method of this class accept a String value as a parameter and adds it to the current StringBuffer object.
The toString() method of this class returns the contents of the current StringBuffer object as a String.
Therefore, to add one string at the starting position of the other −
Get the both strings, suppose we have a string str1 and the string to be added at begin of str1 is str2.
Get the both strings, suppose we have a string str1 and the string to be added at begin of str1 is str2.
Create an empty StringBuffer object.
Create an empty StringBuffer object.
Initially, append str2 to the above created StringBuffer object, using the append() method, Then, append str1.
Initially, append str2 to the above created StringBuffer object, using the append() method, Then, append str1.
Finally, convert the StringBuffer String using the toString() method.
Finally, convert the StringBuffer String using the toString() method.
import java.util.Scanner;
public class StringBufferExample {
   public static void main(String args[]) {
      System.out.println("Enter string1: ");
      Scanner sc= new Scanner(System.in);
      String str1 = sc.next();
      System.out.println("Enter string2: ");
      String str2 = sc.next();
      StringBuffer sb = new StringBuffer();
      sb.append(str2);
      sb.append(str1);
      String result = sb.toString();
      System.out.println(result);
   }
}
Enter string1:
krishna
Enter string2:
kasyap
kasyapkrishna