Java Program to Add Characters to a String

Java provides different ways to add characters to a string. We can add characters in the beginning or at the end or at any position according to the need.

In this article we are going to see three approaches to do so −

• Using ‘+’ operator

• Using methods of StringBuffer and StringBuilder class

• Using substring() method

Approach 1: Using ‘+’ Operator

In this section, we will add a character to a string using the concatenation operator.

Example

public class Main {
   public static void main(String[] args) {
      String st = "Tutorial";
	   char chartoadd = 's';
	   st = st + chartoadd; 
      // performing concatenation
	   System.out.println(st);
   }
} 

Output

Tutorials

Approach 2: Using methods of StringBuilder and StringBuffer class

To understand this section, you need to have a basic understanding of the StringBuilder and StringBuffer classes of Java.

Strings are immutable in java but to perform modification of string, Java provides two inbuilt classes StringBuilder and StringBuffer. Both have insert() and append() methods that can be used to add characters to a string.

insert()

It is present in both classes with a slight difference in that we have to create an object of StringBuilder if we are using the StringBuilder class and create an object of StringBuffer if we are using the StringBuffer class.

The insert() method allow us to add characters at the specified position.

Syntax

public StringBuilder insert(index, char);
public StringBuffer insert(index, char);

Parameters

index − position in the string where you want to add the character.

char − character you want to add.

For StringBuffer

Example

public class Main{
   public static void main(String []args){
      String st="oint";
      char chartoadd='P';
      StringBuffer new_st=new StringBuffer(st);
      new_st.insert(0,chartoadd);
      System.out.println(new_st);
   }
}

Output

Point

‘point’ is the name of the string and ‘P’ is the character we want to add at 0th position. First, we have created an object named ‘new_st’ of StringBuffer class and then we have used insert() method with index value 0 and name of variable that holds character ‘P’.

For StringBuilder

Example

public class Main{
   public static void main(String []args){
      String st="Tutorial";
      char chartoadd='s';
      StringBuilder new_st=new StringBuilder(st);
      new_st.insert(8,chartoadd);
      System.out.println(new_st);
   }
}

Output

Tutorials

‘Tutorial’ is the name of given string and ‘s’ is the character we want to add at the 8th position. First, we have created an object named ‘new_st’ of StringBuilder class and then we have used insert() method with index value 8 and name of variable that holds character ‘s’.

append()

It is also present in both classes with a slight difference in that we have to create an object of StringBuilder if we are using StringBuilder class and create an object of StringBuffer if we are using StringBuffer class.

The append() method will add characters at the end of string.

Syntax

public StringBuffer append(char);
public StringBuilder append(char);

Parameter

char − character you want to add.

For StringBuffer

public class Main{
   public static void main(String []args){
      String st="Simpl";
      char chartoadd='y';
      StringBuffer new_st=new StringBuffer(st);
      new_st.append(chartoadd);
      System.out.println(new_st);
   }
}

Output

Simply

Here, we have created an object named ‘new_st’ of StringBuffer class and then we have used append() method with name of variable that holds character ‘y’. Remember, append() method doesn’t require index value like insert() method.

For StringBuilder

Example

public class Main{
   public static void main(String []args){
      String st="Tutorial";
      char chartoadd='s';
      StringBuilder new_st=new StringBuilder(st);
      new_st.append(chartoadd);
      System.out.println(new_st);
   }
}

Output

Tutorials

We have created an object named ‘new_st’ of StringBuilder class and then we have used append() method with name of variable that holds character ‘s’.

Approach 3: Using substring() method of String class

The String class of Java has a method called substring() that can be used to add characters to a given string.

Syntax

old_string.substring(start_pos, target_pos);

Parameters

start_pos − Start index of the old string

target_pos − Index where you want to add the character.

Example

public class Main{
   public static void main(String []args){
      String st="Tutorialsoint";
      char chartoadd='P';
      String new_st= st.substring(0,9) + chartoadd + st.substring(9);
      System.out.println(new_st);
   }
}

Output

TutorialsPoint

We have created ‘new_st’ as a new concatenated string. First, we have splitted the old string ‘st’ from 0th position to 8th position and then we have added the character at 9th position. At the end, we have added rest of the string.

Conclusion

We have seen different methods to add characters to a string. We can use the concatenation operator, insert() and append() methods. The StringBuilder class is faster than the StringBuffer class but for thread safety, StringBuffer is more secure. If we want to add characters at a specific position then we can prefer insert() method and for adding a character at the end of a string use append() method. At last, we have seen the use substring() method that requires dividing the old string into different parts.