Java Program to Add Characters to a String

We will be discussing out how to add character to a string at particular position in a string in java. It can be interpreted as follows as depicted in the illustration what we are trying to do which is as follows:

Illustration:

Input: 
Input custom string = Hello
Output: 
    --> String to be added 'Geeks'
    --> If end position, Output: HelloGeeks
    --> If in beginning, Output: GeeksHello
    --> If at sat 3rd index, Output: HelGeekslo 

Methods: This can be done using multiple methods of which frequently used methods are listed below as follows:

1. Using + operator
   • At the end
   • At the beginning
2. Using insert() method of StringBuffer class
3. Using substring() method

Let us discuss all three methods above listed in detail to get a fair understanding of the same

Method 1: Using + operator

1.1 At the end

Example: One can add character at the start of String using the ‘+’ operator.

Java

// Java Program to Add Characters to a String
// At the End

// Importing input output classes
import java.io.*;

// Main class
public class GFG {

    // Main driver method
    public static void main(String args[])
    {

        // Input character and string
        char a = 's';
        String str = "GeeksforGeek";

        // Inserting at the end
        String str2 = str + a;

        // Print and display the above string
        System.out.println(str2);
    }
}

Output

GeeksforGeeks

1.2 At the beginning

Example: One can add character at the start of String using the ‘+’ operator. 

Java

// Java Program to Add Characters to a String
// At the Beginning

// Importing input output classes
import java.io.*;

// Main class
public class GFG {

    // Main driver method
    public static void main(String args[])
    {
        // Input character and string
        char a = 'G';
        String str = "eeksforGeeks";

        // Inserting at the beginning
        String str2 = a + str;

        // Print and display the above string
        System.out.println(str2);
    }
}

Output

GeeksforGeeks

Method 2: Using insert() method of StringBuffer class

StringBuffer is a peer class of String that provides much of the functionality of strings. The string represents fixed-length, immutable character sequences while StringBuffer represents grow able and writable character sequences. StringBuffer may have characters and sub-strings inserted in the middle or appended to the end. It will automatically grow to make room for such additions and often has more characters pre-allocated than are actually needed, to allow room for growth. One can use the StringBuffer class method namely the insert() method to add character to String at the given position. This method inserts the string representation of given data type at given position in StringBuffer.

Syntax:

 str.insert(int position,  char x);
 str.insert(int position,  boolean x);
 str.insert(int position,  char[] x);
 str.insert(int position, float x);
 str.insert(int position, double x);
 str.insert(int position, long x);
 str.insert(int position, int x);
position is the index in string where
we need to insert.

Return type: A reference to this object.

Example 

Java

// Java Program to Add Characters to a String
// Using StringBuffer class insert() method

// Main class
// AddCharacterToStringAnyPosition
public class GFG {

    // Method 1
    // To add character to string
    public static String addCharToString(String str, char c,
                                         int pos)
    {

        // Creating an object of StringBuffer class
        StringBuffer stringBuffer = new StringBuffer(str);

        // insert() method where position of character to be
        // inserted is specified as in arguments
        stringBuffer.insert(pos, c);

        // Return the updated string
        // Concatenated string
        return stringBuffer.toString();
    }

    // Method 2
    // Main driver method
    public static void main(String[] args)
    {

        // Input string and character
        String blogName = "GeeksforGeeks";
        char two = 'f';

        // Calling the method 1 to
        // add character to a string

        // Custom string, character and position passed
        String cblogName
            = addCharToString(blogName, two, 5);

        // Print and display th above string
        System.out.println(cblogName);
    }
}

Output

GeeksfforGeeks

Method 3: Using substring() method

One can also use String’s substring method to add character to String at given position. This method has two variants, and it returns a new string that is substring of a string where the substring begins with a character at the specified index and extends to the end of the string.  

Syntax: 

public String substring(int begIndex)

Parameters: The beginning index, inclusive.

Return Value: The specified substring.

Example 

Java

// Java Program to Add Characters to a String
// Using substring() method

// Main class
// AddCharacterToStringAnyPosition
public class GFG {

    // Method 1
    // To add character to a string
    public static String
    addCharToStringUsingSubString(String str, char c,
                                  int pos)
    {
        return str.substring(0, pos) + c
            + str.substring(pos);
    }

    // Method 2
    // Main driver method
    public static void main(String[] args)
    {
        // Custom input character and string
        String blogName = "GeeksforGeeks";
        char two = 'f';

        // Calling the Method 1 to
        // To add character to a string

        // Custom arguments
        String cblogName = addCharToStringUsingSubString(
            blogName, two, 5);

        // Print and display the above string on console
        System.out.println(cblogName);
    }
}

Output

GeeksfforGeeks