What is StringBuilder.charAt in Java?
The charAt method can be used to get the character at the specific index of the string of the StringBuilder.
Syntax
public char charAt(int index);
Such a method returns the character at the passed index.
The index value should be positive and less than the length of the string. Otherwise, IndexOutOfBoundsException will be thrown.
The value of the index argument acts like an array indexing. For example, index 0 denotes the first character.
Code
class CharAtExample {public static void main( String args[] ) {StringBuilder str = new StringBuilder();str.append("Educative");for(int i = 0; i < str.length();i++){char ch = str.charAt(i);System.out.println("The character at index " + i + " is : " + ch);}}}
In the code above, we created a StringBuilder and appended the string "Educative" to it. We then looped the StringBuilder from index 0 and printed the character at each index inside the loop.
Point to be noted
If the character at a specific index is a surrogate, then the surrogate value is returned.
For example:
class CharAtExample {public static void main( String args[] ) {StringBuilder str = new StringBuilder();str.append("😃"); //😃 is equal to 2 characters -- \uD83D\uDE02System.out.println("The character at index 0 is : " + str.charAt(0) +", char code is : " + str.codePointAt(0));System.out.println("The character at index 1 is : " + str.charAt(0) +", char code is : " + str.codePointAt(1));}}
Explanation
In the code above, we did the following:
-
We created a
StringBuilderand appended the😃emoji to it. -
Internally, the
😃is formed by combining two characters\uD83D\uDE02because thechartype in Java is 16-bit, we cannot represent all Unicode characters(like emoji) within the 16-bit. -
The
charAtmethod will return the surrogate value of the\uD83D\uDE02when we ask forcharAt(0). We also printed the code point of the specific character.
Read more about handling emoji here.