4.8. Strings in Expressions

Years of math classes have probably convinced you that it’s possible to add numbers together. What about Strings? Can we add them together? Yup! However, it’s not as fancy a process as adding numbers together; when we add Strings together, we simply squish the strings together, so they become one giant String.

Take a look at this program and try to predict what will be displayed as a result of executing this program (don’t press run until you’re ready to check your answer!):

String firstName = "Greatest";
String lastName = "Ever";
String fullName = firstName + " " + lastName;

System.out.println(fullName);

Take a look at the third line of the program. This statement contains the expression, firstName + " " + lastName. Your computer will simplify this expression by first grabbing the Strings that are referenced by the variables firstName and lastName. Then, your computer will add all of the Strings together to make a new String object. It’s this String that is assigned to the variable fullName.

To summarize, your computer might process this program like so:

Notional machine String concatenation.