Java string charat exception

Java String charAt() Method example

The Java String charAt(int index) method returns the character at the specified index in a string. The index value that we pass in this method should be between 0 and (length of string-1). For example: s.charAt(0) would return the first character of the string represented by instance s. Java String charAt method throws IndexOutOfBoundsException, if the index value passed in the charAt() method is less than zero or greater than or equal to the length of the string ( index<0|| index>=length() ).

Java String charAt() Method example

Lets take an example to understand the use of charAt() method. In this example we have a string and we are printing the 1st, 6th, 12th and 21st character of the string using charAt() method.

public class CharAtExample < public static void main(String args[]) < String str = "Welcome to string handling tutorial"; //This will return the first char of the string char ch1 = str.charAt(0); //This will return the 6th char of the string char ch2 = str.charAt(5); //This will return the 12th char of the string char ch3 = str.charAt(11); //This will return the 21st char of the string char ch4 = str.charAt(20); System.out.println("Character at 0 index is: "+ch1); System.out.println("Character at 5th index is: "+ch2); System.out.println("Character at 11th index is: "+ch3); System.out.println("Character at 20th index is: "+ch4); >>

Character at 0 index is: W Character at 5th index is: m Character at 11th index is: s Character at 20th index is: n

IndexOutOfBoundsException while using charAt() method

When we pass negative index or the index which is greater than length()-1 then the charAt() method throws IndexOutOfBoundsException. In the following example we are passing negative index in the charAt() method, lets see what we get in the output.

Output:

Java String charAt() example to print all characters of string

To print all the characters of a string, we are running a for loop from 0 to length of string – 1 and displaying the character at each iteration of the loop using the charAt() method.

B e g i n n e r s B o o k

Java String charAt() example to count the occurrence of a character

In this example, we will use the charAt() method to count the occurrence of a particular character in the given string. Here we have a string and we are counting the occurrence of character ‘B’ in the string.

public class JavaExample < public static void main(String[] args) < String str = "BeginnersBook"; //initialized the counter to 0 int counter = 0; for (int i=0; i> System.out.println("Char 'B' occurred "+counter+" times in the string"); > >

Output:

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About the Author

I have 15 years of experience in the IT industry, working with renowned multinational corporations. Additionally, I have dedicated over a decade to teaching, allowing me to refine my skills in delivering information in a simple and easily understandable manner.

Comments

yourString.charAt(0); A group of words is simply a string with a couple of blank space characters. The index 0 of the String is your first letter.

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Java String charAt() Method

The method charAt() in Java can be defined as the inbuilt method that returns the character value at the stated index number when searched in a string.

Syntax of charAt() in Java

The syntax of the charAt() in Java is as follow:

where string can be described as an object belonging to the String class.

Parameter of charAt() in Java

The charAt() method in Java has the parameter as an index.

index: The index is defined as the place of the character present in a string as its integer value.

Return Value of charAt() in Java

Return Type : Character

The character present at the specified index is returned.

Java String charAt() Method Example

Let us understand one basic example to explain the method charAt() in Java.

Explanation: As can be seen above we have printed the first and nineteenth characters from the string which says «Learning Java» . Here is the total length of the character in the string is 12 and we have printed the 1st and 8th characters.

Exceptions of charAt() in Java

IndexOutOfBoundsException : Thrown when the index provided is negative or greater than or equal to the length of the string.

What is charAt() in Java?

We can define the charAt() function in Java as the method by which we can return the character value for a particular index number belonging to a string while executing the charAt() method.

As we know while counting the index numbers in Java we start with 0 for specifying the first character, 1 for the second character, and so on.

This index value can be defined to be between 0 and (length of string — 1).

More Examples

Example 1: Java String charAt() Method

Let us understand the charAt() Method by the below example.

Explanation:

Here we are using the charAt() in Java to print the first, ninth, and twelfth characters of the string. As can be seen we used the charAt() in Java and specified the index 0, 8, and 11 respectively as the index value starts from 0 not 1 in Java.

Example 2: Java String charAt — IndexOutOfBoundsException

Let us understand the charAt() Method to understand the IndexOutOfBoundsException by the below example.

Explanation:

Here we see that we get StringIndexOutOfBoundsException as the index that we gave was negative and as we already studied for any index which is negative of more than the range of the index for a string we will get this exception.

Example 3: Java String charAt — Print All Characters of the String

Let us understand the charAt() Method to print all characters of the string with the help of below example.

Explanation:

Here we see that for printing all the characters of a string we have used the logic of loops in Java. We used the for loop to print each index character from the index value ranging from 0 to lengthofstring()-1 . If we exceed that it will definitely give us of bound exception.

Example 4: Java String charAt — Printing the First and Last Character of a String

Let us understand the charAt() Method to print the first and last character of a string with the help of the below example.

Explanation:

Here we are using the charAt() method to print the first and last character of the string. As we already studied the index value in Java starts from 0 and not 1, we use the index value as 0 to print the first character and the length of string-1 to print the last character of the string.

Example 5: Java String charAt — Print Characters Presented at Odd Positions

Let us understand the charAt() Method to print the character present at the odd places of a string with the help of the below example.

Explanation:

Here we have used the for loop along with charAt() in Java to specify a condition of the index value to give output other than 0 which states that those are odd positions and then once we have those index values we then print the values of those characters from the string.

Try yourself by modifying the code to print the characters present on the even position.

Example 6: Java String charAt — Counting the Number of Vowels in a String

Let us understand the charAt() Method to Count Counting the Number of Vowels in a String with the help of the below example.

Explanation: Here we have made the use of charAt() in Java to count the number of vowels in a string.

Example 7: Java String charAt — Counting the Occurrence

Let us understand the charAt() Method to count the Occurrence of a character from a string with the help of the below example.

Explanation:

Here we have counted the occurrence of the character ‘S’ from the string. We have used the for loop with charAt() in Java to increase the counter value every time it sees the character ‘S’ and as shown in the code above we have counted the number of times the letter ‘S’ occurred in the string which in this case was 1.

Conclusion

• The method charAt() in Java can be defined as the inbuilt method that returns the character value at the stated index number when searched in a string.
• The syntax of the charAt() in java is as follow:

• The output for negative integer or out-of-bounds positive integer when passed while executing the charAt() in Java gives the StringIndexOutOfBoundsException exception.
• We have studied so many examples covering a variety of scenarios where we can make use of simple charAt() in Java and simplify our process.

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How to Handle String Index Out Of Bounds Exception in Java

The StringIndexOutOfBoundsException is an unchecked exception in Java that occurs when an attempt is made to access the character of a string at an index which is either negative or greater than the length of the string.

For some methods of the String class, such as the charAt method, this exception is also thrown when the index is equal to the size of the string.

Since the StringIndexOutOfBoundsException is an unchecked exception, it does not need to be declared in the throws clause of a method or constructor. It can be handled in code using a try-catch block.

What Causes StringIndexOutOfBoundsException

A Java string is a collection of characters which has a range of [0, length of string]. When an attempt is made to access the characters with limits that fall outside the range of the string, the StringIndexOutOfBoundsException is thrown. Therefore, this exception occurs when the index of a character does not exist in the string.

Some methods that throw a StringIndexOutOfBoundsException with invalid specified arguments are:

• String.charAt(int index) — Returns the character at the specified index. The index can have a range of [0, length — 1]. If the specified index does not belong to this range, a StringIndexOutOfBoundsException occurs.
• CharSequence.subSequence(int beginIndex, int endIndex) — Returns a new character sequence based on specified arguments. The StringIndexOutOfBoundsException is thrown if any index is negative, the endIndex is greater than the length of the string or the beginIndex is greater than the endIndex .
• String.substring(int beginIndex) — Returns a substring beginning with the character at the specified index. If the beginIndex is negative or greater than the length of the string, a StringIndexOutOfBoundsException is thrown.
• String.substring(int beginIndex, int endIndex) — Returns a substring beginning with the character at the specified index, extending until the character at (endIndex — 1) . The StringIndexOutOfBoundsException is thrown if any index is negative, the endIndex is greater than the length of the string or the beginIndex is greater than the endIndex .
• String.valueOf(char[] data, int offset, int count) — Returns the string representation of the specified character array argument. If any index is negative or if (offset + count) is greater than the size of the specified array, a StringIndexOutOfBoundsException is thrown.

Also, all constructors of the String class that contain an array in their argument list throw a StringIndexOutOfBoundsException when the specified offset and count arguments are invalid.

StringIndexOutOfBoundsException Example

Here is an example of a StringIndexOutOfBoundsException thrown when an attempt is made to retrieve the character at a specified index that falls outside the range of the string:

public class StringIndexOutOfBoundsExceptionExample < public static void main(String args[]) < String str = "My String"; System.out.println(str.charAt(9)); > >

In this example, the String.charAt() method is used to access the character at index 9. Since this method only allows a range of [0, length — 1] for the string, using index 9 throws the StringIndexOutOfBoundsException as it falls outside the range:

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 9 at java.base/java.lang.StringLatin1.charAt(StringLatin1.java:48) at java.base/java.lang.String.charAt(String.java:711) at StringIndexOutOfBoundsExceptionExample.main(StringIndexOutOfBoundsExceptionExample.java:4)

How to Handle StringIndexOutOfBoundsException

The StringIndexOutOfBoundsException is an exception in Java, and therefore can be handled using try-catch blocks using the following steps:

• Surround the statements that can throw an StringIndexOutOfBoundsException in try-catch blocks
• Catch the StringIndexOutOfBoundsException
• Depending on the requirements of the application, take necessary action. For example, log the exception with an appropriate message.
• Check the length of the string using String.length() and access its characters that fall within the range.

The code in the earlier example can be updated with the above steps:

public class StringIndexOutOfBoundsExceptionExample < public static void main(String args[]) < String str = "My String"; try < System.out.println(str.charAt(9)); > catch(StringIndexOutOfBoundsException e) < System.out.println("String index out of bounds. String length: " + str.length()); > > >

Surrounding the code in try-catch blocks like the above allows the program to continue execution after the exception is encountered:

String index out of bounds. String length: 9

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