Insert a String into another String in Java

Given a String, the task is to insert another string in between the given String at a particular specified index in Java.

Examples:

Input: originalString = "GeeksGeeks", 
              stringToBeInserted = "For", 
              index = 4
Output: "GeeksForGeeks"


Input: originalString = "Computer Portal", 
              stringToBeInserted = "Science ", 
              index = 8
Output: "Computer Science Portal"

The various methods to do this are as follows:

1. Without using any pre-defined method

   Approach:

   1. Get the Strings and the index.
   2. Create a new String
   3. Traverse the string till the specified index and copy this into the new String.
   4. Copy the String to be inserted into this new String
   5. Copy the remaining characters of the first string into the new String
   6. Return/Print the new String

   Below is the implementation of the above approach:

   Program:

   
   

   
   
   

   // Java program to insert a string into another string // without using any pre-defined method    import java.lang.*;    class GFG {        // Function to insert string     public static String insertString(         String originalString,         String stringToBeInserted,         int index)     {            // Create a new string         String newString = new String();            for (int i = 0; i < originalString.length(); i++) {                // Insert the original string character             // into the new string             newString += originalString.charAt(i);                if (i == index) {                    // Insert the string to be inserted                 // into the new string                 newString += stringToBeInserted;             }         }            // return the modified String         return newString;     }        // Driver code     public static void main(String[] args)     {            // Get the Strings         String originalString = "GeeksGeeks";         String stringToBeInserted = "For";         int index = 4;            System.out.println("Original String: "                            + originalString);         System.out.println("String to be inserted: "                            + stringToBeInserted);         System.out.println("String to be inserted at index: "                            + index);            // Insert the String         System.out.println("Modified String: "                            + insertString(originalString,                                           stringToBeInserted,                                           index));     } }
   Output:

   Original String: GeeksGeeks
   String to be inserted: For
   String to be inserted at index: 4
   Modified String: GeeksForGeeks
   

2. Using String.substring() method

   Approach:

   1. Get the Strings and the index.
   2. Create a new String
   3. Insert the substring from 0 to the specified (index + 1) using substring(0, index+1) method. Then insert the string to be inserted into the string. Then insert the remaining part of the original string into the new string using substring(index+1) method.
   4. Return/Print the new String

   Below is the implementation of the above approach:

   Program:

   
   

   
   
   

   // Java program to insert a string into another string // without using any pre-defined method    import java.lang.*;    class GFG {        // Function to insert string     public static String insertString(         String originalString,         String stringToBeInserted,         int index)     {            // Create a new string         String newString = originalString.substring(0, index + 1)                            + stringToBeInserted                            + originalString.substring(index + 1);            // return the modified String         return newString;     }        // Driver code     public static void main(String[] args)     {            // Get the Strings         String originalString = "GeeksGeeks";         String stringToBeInserted = "For";         int index = 4;            System.out.println("Original String: "                            + originalString);         System.out.println("String to be inserted: "                            + stringToBeInserted);         System.out.println("String to be inserted at index: "                            + index);            // Insert the String         System.out.println("Modified String: "                            + insertString(originalString,                                           stringToBeInserted,                                           index));     } }
   Output:

   Original String: GeeksGeeks
   String to be inserted: For
   String to be inserted at index: 4
   Modified String: GeeksForGeeks
   

3. Using StringBuffer.insert() method

   Approach:

   1. Get the Strings and the index.
   2. Create a new StringBuffer
   3. Insert the stringToBeInserted into the original string using StringBuffer.insert() method.
   4. Return/Print the String from the StringBuffer using StringBuffer.toString() method.

   Below is the implementation of the above approach:

   Program:

   
   

   
   
   

   // Java program to insert a string into another string // without using any pre-defined method    import java.lang.*;    class GFG {        // Function to insert string     public static String insertString(         String originalString,         String stringToBeInserted,         int index)     {            // Create a new StringBuffer         StringBuffer newString             = new StringBuffer(originalString);            // Insert the strings to be inserted         // using insert() method         newString.insert(index + 1, stringToBeInserted);            // return the modified String         return newString.toString();     }        // Driver code     public static void main(String[] args)     {            // Get the Strings         String originalString = "GeeksGeeks";         String stringToBeInserted = "For";         int index = 4;            System.out.println("Original String: "                            + originalString);         System.out.println("String to be inserted: "                            + stringToBeInserted);         System.out.println("String to be inserted at index: "                            + index);            // Insert the String         System.out.println("Modified String: "                            + insertString(originalString,                                           stringToBeInserted,                                           index));     } }
   Output:

   Original String: GeeksGeeks
   String to be inserted: For
   String to be inserted at index: 4
   Modified String: GeeksForGeeks