Beginning Programming with Java For Dummies
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Most Java programs don’t work correctly the first time you run them, and some programs don’t work without extensive trial and error on your part. This code is a case in point.

To write this code, you need a way to generate three-letter words randomly. This code would give you the desired result:

anAccount.lastName = " +
 (char) (myRandom.nextInt(26) + 'A') +
 (char) (myRandom.nextInt(26) + 'a') +
 (char) (myRandom.nextInt(26) + 'a');
Here’s how the code works:
  • Each call to the Random.nextInt(26) generates a number from 0 to 25.

  • Adding 'A' gives you a number from 65 to 90.

    To store a letter 'A', the computer puts the number 65 in its memory. That’s why adding 'A' to 0 gives you 65 and why adding 'A' to 25 gives you 90.

  • Applying (char) to a number turns the number into a char value.

    To store the letters 'A' through 'Z', the computer puts the numbers 65 through 90 in its memory. So applying (char) to a number from 65 to 90 turns the number into an uppercase letter.

Pause for a brief summary. The expression (char) (myRandom.nextInt(26) + 'A') represents a randomly generated uppercase letter. In a similar way, (char) (myRandom.nextInt(26) + 'a') represents a randomly generated lowercase letter.

Watch out! The next couple of steps can be tricky.

  • Java doesn’t allow you to assign a char value to a string variable.

    The following statement would lead to a compiler error:

    //Bad statement:
    anAccount.lastName = (char) (myRandom.nextInt(26) + 'A');
  • In Java, you can use a plus sign to add a char value to a string. When you do, the result is a string.

    So "" + (char) (myRandom.nextInt(26) + 'A') is a string containing one randomly generated uppercase character. And when you add (char) (myRandom.nextInt(26) + 'a') onto the end of that string, you get another string — a string containing two randomly generated characters

    Finally, when you add another (char) (myRandom.nextInt(26) + 'a') onto the end of that string, you get a string containing three randomly generated characters. So you can assign that big string to anAccount.lastName. That’s how the statement works.

When you write a program, you have to be very careful with numbers, char values, and strings. This isn’t the kind of programming you do every day of the week, but it is a lesson that you need to be persistent in your Java programming.

About This Article

This article is from the book:

About the book author:

Dr. Barry Burd holds an M.S. in Computer Science from Rutgers University and a Ph.D. in Mathematics from the University of Illinois. Barry is also the author of Beginning Programming with Java For Dummies, Java for Android For Dummies, and Flutter For Dummies.

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