In Java, the symbol + can be used to add numbers or to concatenate strings. This exercise illustrates both uses.When using a string literal (a sequence of characters enclosed in double quotation marks) in Java the complete string must fit on one line. The following is NOT legal (it would result in a compile-time error). System.out.println ("It is NOT okay to go to the next line in a LONG string!!!");

The solution is to break the long string up into two shorter strings that are joined using the concatenation operator (which is the + symbol). This is discussed in Section 2. 1 in the text. So the following would be legal System.out.println ("It is OKAY to break a long string into " + "parts and join them with a + symbol."); So, when working with strings the + symbol means to concatenate the strings (join them). BUT, when working with numbers the + means what it has always meant—add!

1.

Observing the Behavior of

+ To see the behavior of + in different settings do the following:

a. Study the program below, which is in file

PlusTest.java.

// ************************************************************

//

PlusTest.java

//

// Demonstrate the different behaviors of the + operator

// ************************************************************

public class PlusTest

{

// -------------------------------------------------

// main prints some expressions using the + operator

// -------------------------------------------------

public static void main (String[] args)

{

System.out.println ("This is a long string that is the " + "concatenation of two shorter strings.");

System.out.println ("The first computer was invented about" + 55 + "years ago.");

System.out.println ("8 plus 5 is " + 8 + 5);

System.out.println ("8 plus 5 is " + (8 + 5)) ;

System.out.println (8 + 5 + " equals 8 plus 5.");

}

}

b. Save PlusTest.java to your directory.

c. Compile and run the program. For each of the last three output statements (the ones dealing with 8 plus 5) write down what was printed. Now for each explain why the computer printed what it did given that the following rules are used for +. Write out complete explanations.