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This example is for Wiring version 1.0 build 0100+. If you have a previous version, use the examples included with your software. If you see any errors or have comments, please let us know.

Adding Strings together by Tom Igoe
Examples of how to add strings together You can also add several different data types to string, as shown here:

    // declare three strings:
    String stringOne, stringTwo, stringThree;

    void setup()
    {
      Serial.begin(9600);
      stringOne = String("stringThree = ");
      stringTwo = String("this string");
      stringThree = String();
      Serial.println("\n\nAdding strings together (concatenation):");
    }

    void loop()
    {
      // adding a constant integer to a string:
      stringThree =  stringOne + 123;
      Serial.println(stringThree);    // prints "stringThree = 123"

      // adding a constant long interger to a string:
      stringThree = stringOne + 123456789;
      Serial.println(stringThree);    // prints " You added 123456789"

      // adding a constant character to a string:
      stringThree =  stringOne + 'A';
      Serial.println(stringThree);    // prints "You added A"

      // adding a constant string to a string:
      stringThree =  stringOne +  "abc";
      Serial.println(stringThree);    // prints "You added abc"

      stringThree = stringOne + stringTwo;
      Serial.println(stringThree);    // prints "You added this string"

      // adding a variable integer to a string:
      int sensorValue = analogRead(A0);
      stringOne = "Sensor value: ";
      stringThree = stringOne  + sensorValue;
      Serial.println(stringThree);    // prints "Sensor Value: 401" or whatever value analogRead(A0) has

      // adding a variable long integer to a string:
      long currentTime = millis();
      stringOne = "millis() value: ";
      stringThree = stringOne + millis();
      Serial.println(stringThree);    // prints "The millis: 345345" or whatever value currentTime has

      // do nothing while true:
      while (true);
    }