String Replace Function

The String replace() function allows you to replace all instances of a given character with another character. You can also use replace to replace substrings of a string with a different substring.

Relevant Groundwork


Hardware Required

  • MSP-EXP430G2 LaunchPad


Only LaunchPad is required for this example.

Blink bb

Image developed using Fritzing. For more circuit examples, see the Fritzing project page.


Blink schem

Code Explanation

Caution: If you try to replace a substring that’s more than the whole string itself, nothing will be replaced. For example:

  String stringOne = "dog";
  String stringTwo = stringOne.replace("twodogs", "Blah");

In this case, the code will compile, but stringOne will remain unchanged, since the replacement substring is more than the String itself.


  String replace()

 Examples of how to replace characters or substrings of a string

 created 27 July 2010
 modified 2 Apr 2012
 by Tom Igoe

 This example code is in the public domain.

void setup() {
  // Open serial communications and wait for port to open:

  // send an intro:
  Serial.println("\n\nString  replace:\n");

void loop() {
  String stringOne = "<HTML><HEAD><BODY>"";
  // replace() changes all instances of one substring with another:
  // first, make a copy of th original string:
  String stringTwo = stringOne;
  // then perform the replacements:
  stringTwo.replace("<", "</");
  // print the original:
  Serial.println("Original string: " + stringOne);
  // and print the modified string:
  Serial.println("Modified string: " + stringTwo);

  // you can also use replace() on single characters:
  String normalString = "bookkeeper";
  Serial.println("normal: " + normalString);
  String leetString = normalString;
  leetString.replace('o', '0');
  leetString.replace('e', '3');
  Serial.println("l33tspeak: " + leetString);

  // do nothing while true:

Working Video

Try it out

  • Replace all the nouns in a string with funny names.

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