Double total, meal, tax;

meal = 20.00;          // autobox the 20.0
tax  = meal*0.12;      // unbox meal, do the math, autobox the product
total = meal+tax;      // unbox meal and tax, do the math, autobox the total

System.out.println("Total Cost: " + total );   // unbox total, convert to String, concatenate

Phone Book Application

ArrayLists are especially convenient when you want to maintain a list of your own object types. Let us develop an application that maintains a phone book. Each entry in the phone book contains a name and a number along with various methods.

class Entry
{
  private String name;
  private String number;

  // constructor
  public Entry( String n, String num )
  {
    name = n; number = num;
  }

  // various methods
  . . .
}

The program will maintain an ArrayList of phone book entries. The user will type in a name and get a phone number.

Enter name --> Hal
Name: Hal; Number: 789-1234

Enter name --> Amy
Name: Amy; Number: 123-4567

Enter name --> quit