How to Use Java String Class charAt() Method

Function Description

The Java String class charAt() method is used to get the character of a string at the specified index. The first character of the string is at index 0 and the last character of the string is at index string_length-1. Index range is from 0 to string_legth-1

Method  Signature

public char charAt(int index)

Parameter

int type index value. The first char value is at index 0. The valid maximum Index number for a particular string is string_length-1

Return Type

char value at the specified index

Exception

Throws StringIndexOutOfBounds Exception if the passing index value is negative or greater than string_length-1

Example of Java String Class charAt() Method

Example to get the character from the string at index 0, 6, 16 and last index

public class ExampleStringCharAt {
    private void getCharcters() {
    String str = "Welcome to string functions learning";
   
    //returns the first character of the string or character at index 0
    char character1 = str.charAt(0);
         
    //returns the 7th character of the string or character at index 6
    char character2 = str.charAt(6);
         
    //returns the 17th character of the string or character at index 16
    char character3 = str.charAt(16);
         
    //returns the last character of the string or character at last index
    char character4 = str.charAt(str.length() -1);
         
    System.out.println("Character at first position = " + character1);
    System.out.println("Character at 7th position = " + character2);
    System.out.println("Character at 17th position = "+ character3);
    System.out.println("Character at last position = " + character4);
    }
     
    public static void main(String[] args) {
          ExampleStringCharAt exampleStringCharAt = new ExampleStringCharAt();
          exampleStringCharAt.getCharcters();
    }
}
 
OutPut :
Character at first position = W
Character at 7th position = e
Character at 17th position = g
Character at last position = g

Example of using the invalid index number:

public class ExampleStringCharAt {

    private void getCharcters() {

    String str = "Welcome to string functions learning";

    //throw exception as passing index value is negative

    System.out.println("passing negative index value = " + str.charAt(-1));
   
    }
   
    public static void main(String[] args) {

          ExampleStringCharAt exampleStringCharAt = new ExampleStringCharAt();

          exampleStringCharAt.getCharcters();
    }
}
 
Output : As index value is invalid it will throw StringIndexOfBoundException

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -1

    at java.lang.String.charAt (String.java:658)

    at com.java.test.exception.ExampleStringCharAt.getCharcters (ExampleStringCharAt.java:7)

    at com.java.test.exception.ExampleStringCharAt.main
 (ExampleStringCharAt.java:13)

Other Methods of String Class

SequenceMethodDescription
1int length()Returns the number of characters count  in  a string.
2static String format(String format, Object… args)Return the formatted String. It is a static method and formats the string as per passing format and argument(s).
3static String format(Locale l, String format, Object… args)Return the formatted String. It is a static method and formats the string as per passing format and argument(s) and locale.
4String substring(int beginIndex)Returns substring from the given index position to the end index of the string.
5String substring(int beginIndex, int endIndex)Returns substring from the specified begin index to the specified end index.
6boolean contains(CharSequence s)Returns boolean value(true/false). It searches the given sequence of characters within the string and returns true/false accordingly. Characters will be case sensitive while searching in string.
7static String join(CharSequence delimiter, CharSequence… elements)Returns joined string. This method joins each passing String using the specified delimiter. It is a static method.
8static String join(CharSequence delimiter, Iterable<? extends CharSequence> elements)Returns the joined string. This method joins each passing string object of an iterate object using the specified delimiter and returns the concatenated string. It is a static method.
9boolean equals(Object another)Returns boolean value(true/false). It checks the equality of string with the passing object.
10boolean isEmpty()Returns boolean value(true/false). It returns true if the string is empty otherwise returns false.
11String concat(String str)Returns the concatenating string. It concatenates the passing string at the end of the string.
12String replace(char old, char new)Return the replaced string. It replaces all occurrences of the specified character with the new character.
13String replace(CharSequence old, CharSequence new)Return the replaced string. It replaces all occurrences of the specified Character sequence with the specified new Character sequence.
14String replaceAll(String regex, String replacement)Returns the replaced string. It replaces all occurrences of the sequence of characters with the given replacement string that are matching with the given regular expression.
15String replaceFirst(String regex, String replacement)Returns the replaced string. It replaces the first matching sequence of characters with the replacement string that matches with the given regular expression.
16static boolean equalsIgnoreCase(String another)Returns the boolean (true/false) value. It compares the passing string with string by ignoring the case. It  compares the content irrespective of lowercase or uppercase of the character(s).
17String[] split(String regex)Returns the array of strings resulting from splitting of the string     around matches of the given regular expression. String is breaked into strings from all  the matching regular expressions.
18String[] split(String regex, int limit)Returns the array of strings resulting from splitting of the string     around matches of the given regular expression. It breaks the string from all the matching regular expression upto the given limit.
19String intern()Returns an interned string. This method helps to compare two objects using == operator and checks in a string constant pool. it is faster for comparison.
20int indexOf(int ch)Returns the index value of first occurrence of the specified character within the string
21int indexOf(int ch, int fromIndex)Returns the index value of first occurrence of the specified character from the substring starting from specified index
22int indexOf(String substring)Returns the index value of first occurrence of the specified substring within the string.
23int indexOf(String substring, int fromIndex)Returns the index value of the first occurrence of the specified string within the substring starting from specified index to end of the string index.
24int lastIndexOf(int ch)Returns the index value of last occurrence of the specified character
25int lastIndexOf (int ch, int fromIndex)Returns the index value of last occurrence of the specified character, search starts at given fromIndex. 
26int lastIndexOf (String str)Returns the index value of last occurrence of the specified string.
27int lastIndexOf (String str, int fromIndexReturns the index value of last occurrence of the specified string, searches start from given fromIndex
28String toLowerCase()Returns all the characters of the string in lowercase .
29String toLowerCase(Locale l)Returns all the characters of the string in lowercase using specified locale.
30String toUpperCase()Returns all the characters of the string in uppercase.
31String toUpperCase(Locale l)Returns all the characters of the string in uppercase using specified locale.
32String trim()Returns the string after removing the white space from the beginning and end of the string.
33static String valueOf(int value)Return the converted string. It converts the objects and all primitive types of values into string. It is a static method.

In this article, we learned all about the charAt() method of String class with example. Apart from charAt() method we got an idea about other String methods too. We will come up with more articles explaining other String methods with examples. For more details please click on the respective methods link.

This article was written by Renu Singh

14+ Years of experience in various phases of the software development life cycle. Specialties: Java/J2EE, Struts, Hibernate, JSF, JSP, Servlets, AJAX, Oracle, Oracle Knowledge, SQL Server 2000, DB2, EJB3.0. Companies Worked For: 1) Tata Consultancy Services 2) Infogain 3) TS Infotech 4) Daffodil Software Ltd.

Leave a Reply

Your email address will not be published. Required fields are marked *