String Character Functions

The String functions charAt() and setCharAt() are used to get or set the value of a character at a given position in a String.

At their simplest, these functions help you search and replace a given character. For example, the following replaces the colon in a given String with an equals sign:

String reportString = "SensorReading: 456";
int colonPosition = reportString.indexOf(':');
reportString.setCharAt(colonPosition, '=');

Here's an example that checks to see if the first letter of the second word is 'B':

String reportString = "Franklin, Benjamin";
int spacePosition = reportString.indexOf(' ');
if (reportString.charAt(spacePosition + 1) == 'B') {
Serial.println("You might have found the Benjamins.")
}

Caution: If you try to get the charAt or try to setCharAt() a value that's longer than the String's length, you'll get unexpected results. If you're not sure, check to see that the position you want to set or get is less than the string's length using the length() function.

Hardware Required

• Arduino Board

Circuit

There is no circuit for this example, though your board must be connected to your computer via USB and the serial monitor window of the Arduino Software (IDE) should be open.

Code

See Also

• String object - Your Reference for String objects

• CharacterAnalysis - We use the operators that allow us to recognise the type of character we are dealing with.

• StringAdditionOperator - Add strings together in a variety of ways.

• StringAppendOperator - Use the += operator and the concat() method to append things to Strings

• StringCaseChanges - Change the case of a string.

• StringComparisonOperators - Get/set the value of a specific character in a string.

• StringConstructors - Initialize string objects.

• StringIndexOf - Look for the first/last instance of a character in a string.

• StringLength - Get the length of a string.

• StringLengthTrim - Get and trim the length of a string.

• StringReplace - Replace individual characters in a string.

• StringStartsWithEndsWith - Check which characters/substrings a given string starts or ends with.

• StringSubstring - Look for "phrases" within a given string.

• StringToInt - Allows you to convert a String to an integer number.

Last revision 2015/08/11 by SM