Java String charAt()

The Java String class charAt() method returns a char value at the given index number.

The index number starts from 0 and goes to n-1, where n is the length of the string. It returns StringIndexOutOfBoundsException, if the given index number is greater than or equal to this string length or a negative number.

Syntax

The method accepts index as a parameter. The starting index is 0. It returns a character at a specific index position in a string. It throws StringIndexOutOfBoundsException if the index is a negative value or greater than this string length.

Specified by

CharSequence interface, located inside java.lang package.

Internal implementation

  public char charAt(int index) {           if ((index < 0) || (index >= value.length)) {               throw new StringIndexOutOfBoundsException(index);           }           return value[index];       }    

Java String charAt() Method Examples

Let’s see Java program related to string in which we will use charAt() method that perform some operation on the give string.

FileName: CharAtExample.java

  public class CharAtExample{  public static void main(String args[]){  String name=”tutoraspire”;  char ch=name.charAt(4);//returns the char value at the 4th index  System.out.println(ch);  }}  

Test it Now

Output:

Let’s see the example of the charAt() method where we are passing a greater index value. In such a case, it throws StringIndexOutOfBoundsException at run time.

FileName: CharAtExample.java

  public class CharAtExample{  public static void main(String args[]){  String name=”tutoraspire”;  char ch=name.charAt(10);//returns the char value at the 10th index  System.out.println(ch);  }}  

Output:

Exception in thread "main" java.lang.StringIndexOutOfBoundsException:   String index out of range: 10  at java.lang.String.charAt(String.java:658)  at CharAtExample.main(CharAtExample.java:4)

Accessing First and Last Character by Using the charAt() Method

Let’s see a simple example where we are accessing first and last character from the provided string.

FileName: CharAtExample3.java

  public class CharAtExample3 {  public static void main(String[] args) {      String str = “Welcome to TutorAspire portal”;          int strLength = str.length();          // Fetching first character      System.out.println(“Character at 0 index is: “+ str.charAt(0));          // The last Character is present at the string length-1 index      System.out.println(“Character at last index is: “+ str.charAt(strLength-1));          }  }  

Output:

Character at 0 index is: W  Character at last index is: l

Print Characters Presented at Odd Positions by Using the charAt() Method

Let’s see an example where we are accessing all the elements present at odd index.

FileName: CharAtExample4.java

  public class CharAtExample4 {  public static void main(String[] args) {  String str = “Welcome to TutorAspire portal”;  for (int i=0; i<=str.length()-1; i++) {  if(i%2!=0) {  System.out.println(“Char at “+i+” place “+str.charAt(i));  }  }  }  }  

Output:

Char at 1 place e  Char at 3 place c  Char at 5 place m  Char at 7 place    Char at 9 place o  Char at 11 place J  Char at 13 place v  Char at 15 place t  Char at 17 place o  Char at 19 place n  Char at 21 place    Char at 23 place o  Char at 25 place t  Char at 27 place l

The position such as 7 and 21 denotes the space.

Counting Frequency of a character in a String by Using the charAt() Method

Let’s see an example in which we are counting frequency of a character in the given string.

FileName: CharAtExample5.java

  public class CharAtExample5 {  public static void main(String[] args) {  String str = “Welcome to TutorAspire portal”;  int count = 0;  for (int i=0; i<=str.length()-1; i++) {  if(str.charAt(i) == ‘t’) {  count++;  }  }  System.out.println(“Frequency of t is: “+count);  }  }  

Output:

Frequency of t is: 4

Counting the Number of Vowels in a String by Using the chatAt() Method

Let’s see an example where we are counting the number of vowels present in a string with the help of the charAt() method.

FileName: CharAtExample6.java

  // import statement  import java.util.*;    public class CharAtExample6  {    ArrayList al;    // constructor for creating and   // assigning values to the ArrayList al  CharAtExample6()  {  al = new ArrayList();    al.add(‘A’); al.add(‘E’);  al.add(‘a’); al.add(‘e’);  al.add(‘I’); al.add(‘O’);  al.add(‘i’); al.add(‘o’);  al.add(‘U’); al.add(‘u’);  }     // a method that checks whether the character c is a vowel or not     private boolean isVowel(char c)  {  for(int i = 0; i < al.size(); i++)  {  if(c == al.get(i))  {  return true;  }  }  return false;  }  // a method that calculates vowels in the String s  public int countVowels(String s)  {  int countVowel = 0; // store total number of vowels  int size = s.length(); // size of string  for(int j = 0; j < size; j++)  {  char c = s.charAt(j);  if(isVowel(c))  {  // vowel found!  // increase the count by 1  countVowel = countVowel + 1;  }  }    return countVowel;  }        // main method  public static void main(String argvs[])   {    // creating an object of the class CharAtExample6  CharAtExample6 obj = new CharAtExample6();    String str = “Tutoraspire is a great site for learning Java.”;      int noOfVowel = obj.countVowels(str);    System.out.println(“String: ” + str);    System.out.println(“Total number of vowels in the string are: “+ noOfVowel + “n”);      str = “One apple in a day keeps doctor away.”;    System.out.println(“String: ” + str);    noOfVowel = obj.countVowels(str);    System.out.println(“Total number of vowels in the string are: “+ noOfVowel);   }    }    

Output:

String: TutorAspire is a great site for learning Java.  Total number of vowels in the string are: 16    String: One apple in a day keeps doctor away.  Total number of vowels in the string are: 13

Next TopicJava String compareTo

charAt()example java method signature string

Java String charAt() method

Java String charAt()

Syntax

Internal implementation

Java String charAt() Method Examples

Accessing First and Last Character by Using the charAt() Method

Print Characters Presented at Odd Positions by Using the charAt() Method

Counting Frequency of a character in a String by Using the charAt() Method

Counting the Number of Vowels in a String by Using the chatAt() Method

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