How To Implement charAt In Java?

The charAt() in Java is a method, used particularly to return the character at the specified index in a string. In this article we will understand this topic in detail. Following pointers will be covered in this article,

• charAt in Java
• Example for StringIndexOutOfBoundsException
• Printing all characters of a string using charAt()
• Counting the frequency of a character using charAt()
• Printing the first and last character of a string

So let us get started

charAt in Java

For charAt() method, the index value passed must be between 0 and (length of string – 1). In case the index value is greater than, equal to, or a negative number, a StringIndexOutOfBoundsException is returned.

Signature

public char charAt(int index)

Parameter

index: The index of the character to be returned

Return

The character at the specified position is returned.

Exception

StringIndexOutOfBoundException: Returned if the value of the index is negative, greater than, or equal to the length of the string.

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Example

public class Main
{
public static void main(String args[])
{
String str = "We must save the planet from climate change";
//This returns the first character of the string
char c1 = str.charAt(0);
char c2 = str.charAt(5);
char c3 = str.charAt(9);
char c4 = str.charAt(15);
System.out.println("Character at 0 index : "+c1);
System.out.println("Character at 5th index : "+c2);
System.out.println("Character at 9th index : "+c3);
System.out.println("Character at 15th index : "+c4);
}
}

Output

Character at 0 index is: W

Character at 5th index is: s

Character at 11th index is: a

Character at 20th index is: e

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Example for StringIndexOutOfBoundsException

On passing a negative index, or index greater than length() – 1 , then a StringIndexOutOfBoundsException is thrown.

In the following example, a negative index is passed: 

public class Main
{
public static void main(String args[])
{
String str = "ClimateChange";
//negative index
char c = str.charAt(-1);
System.out.println(c);
}
}

Output

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

at java.base/java.lang.StringLatin1.charAt(tringLatin1.java:44)

at java.base/java.lang.String.charAt(String.java:692)

at Main.main(Main.java:5)

Command exited with non-zero status 1

The code terminates with an exception.

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Printing all characters of a string using charAt()

The usage of for loop from 0 to the length of string() -1 is made, to print all characters of a string.

</p>
public class Main
{
public static void main(String args[])
{
String s = "ClimateChange";
for(int i=0; i<=s.length()-1; i++) {
System.out.println(s.charAt(i));
}
}
}
<p style="text-align: justify;">

Output

C

l

i

m

a

t

e

C

h

a

n

g

e

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Counting the frequency of a character using charAt()

public class Main
{
public static void main(String[] args)
{
String s = "ClimateChangeIsReal";
int count = 0;
for (int i=0; i<=s.length()-1; i++)
{
if(s.charAt(i) == 'C'){
count++;
}
}
System.out.println("Frequency of C is: "+count);
}
}

The frequency of a character can be determined by using charAt():

 Output

Frequency of C is: 2

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Printing the first and last character of a string

The first and the last character of a string can be printed using charAt():

public class Main
{
public static void main(String[] args)
{
String s = "Climate Change Is Real";
int strLength = s.length();
//first character
System.out.println("Character at 0 index : "+ s.charAt(0));
//Fetching last Character present at the string length-1 index
System.out.println("Character at last index : "+ s.charAt(strLength-1));
}
}

Output

Character at 0 index : C

Character at last index : l

The charAt() method provides the user with innumerous ways to access the elements at any specified index, as long as the index falls within an appropriate range.

Thus we have come to an end of this article on ‘charAt in Java’. If you wish to learn more, check out the Java Training by Edureka, a trusted online learning company. Edureka’s Java J2EE and SOA training and certification course is designed to train you for both core and advanced Java concepts along with various Java frameworks like Hibernate & Spring.

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