Java StringBuilder setCharAt() method

The setCharAt(int index, char ch) method of Java StringBuilder class is used to set the specified character at the given index. The specified character altered this sequence by replacing the old character at the given index.

Syntax:

Parameter:

DataType	Parameter	Description
int	index	It is the index of character which is to modify.
char	ch	A new character which modifies the old character at the given index.

Returns:

Exception:

IndexOutOfBoundsException - if an index is negative or greater than or equal to length() of this sequence.

Compatibility Version:

Java 1.5 and above

Example 1

public class StringBuilderSetCharAtExample1 {
	public static void main(String[] args) {
	      StringBuilder sb = new StringBuilder("abc");
	      System.out.println("string = " + sb);
	      // character at index 1
	      System.out.println("character at index 1 = " + sb.charAt(1));
	      // set character at index 1
	      sb.setCharAt(1, 'x');
	      System.out.println("new string = " + sb);
	      // character at index 1
	      System.out.println("character at index 1 = " + sb.charAt(1));
	}
}

Test it Now

Output:

string = abc
character at index 1 = b
new string = axc
character at index 1 = x

Example 2

public class StringBuilderSetCharAtExample2 {
	public static void main(String[] args) {
	      StringBuilder sb = new StringBuilder("abc");
	      System.out.println("string = " + sb);
	      // try to set character at index 3 > length throw exception
	      sb.setCharAt(3,'x');
	      System.out.println("character at index 1 = " +sb);
	 }
}

Test it Now

Output:

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 3
	at java.lang.AbstractStringBuilder.setCharAt(Unknown Source)
	at java.lang.StringBuilder.setCharAt(Unknown Source)
	at snippet.StringBuilderSetCharAtExample2.main(StringBuilderSetCharAtExample2.java:6)
string = abc

Example 3

public class StringBuilderSetCharAtExample3 {
	public static void main(String[] args) {
	   StringBuilder sb = new StringBuilder("");
	    
	    System.out.print("enter your string value: ");
	    Scanner sc = new Scanner(System.in);
	    sb.append(sc.nextLine());
	  
                  System.out.print("enter index value: ");
                  int index = sc.nextInt(); 
                 System.out.print("enter character value: ");
                 char ch = sc.next().charAt(0);
	    // set character at input index
	    sb.setCharAt(index, ch);
	    System.out.println("new string = " + sb);
	    sc.close();
		
	}
}

Test it Now

Output:

enter your string value: Java
enter index value: 0
enter character value: j
new string = java

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Java StringBuilder setCharAt() method

Syntax:

Parameter:

Returns:

Exception:

Compatibility Version:

Example 1

Example 2

Example 3

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