1. Outline Creating Objects The String Class Packages Formatting Output
Enumerated Types
Wrapper Classes
Components and Containers
Images

2. Formatting output It is often necessary to format values
output looks appropriate when printed or displayed
NumberFormat part of java.text package
Provides generic formatting capabilities
is not instantiated using the new operator
instead by requesting an object
From one of the static methods invoked thru the class name
NumberFormat fmt = NumberFormat.getCurrencyInstance();

3. Creating NumberFormat instance
NumberFormat objects
are created using
getCurrencyInstance() invoked thru class name
returns a formatter for monetary values
getPercentInstance() invoked thru class name
returns an object that formats a percentage
are used to format numbers using method format()
Refer to Purchase.java
NumberFormat fmt = NumberFormat.getCurrencyInstance()
double subtotal=19.35;
System.out.println(fmt.format(subtotal) );
Output: $19.35

4. DecimalFormat class DecimalFormat part of java.text package
allows to format values based on a pattern
To determine how many digits should be printed
To the right of the decimal point (for instance)
is instantiated in the traditional way
using the new operator
Its constructor DecimalFormat takes a String
That represents a pattern for the formatted number
Refer to CircleStats.java

5. Outline Creating Objects The String Class Packages Formatting Output
Enumerated Types
Wrapper Classes
Components and Containers
Images

6. Enumerated types Java allows you to define an enumerated type
Which can then be used to declare variables
as the type of a variable
establishes all possible values for a variable of that type
By listing, or enumerating the values
Where the values are identifiers, and can be anything desired
enum Season {winter, spring, summer, fall}
There is no limit to the number of listed values
Any number of values can be listed

7. Declaring and using an enumerated type
Once a type is defined
A variable of that type can be declared
enum Grade {A, B, C, D, F};
Grade score;
And it can be assigned a value
Thru the name of the type
score = Grade.A;
Enumerated types are type-safe
You cannot assign any value other than those listed

8. Ordinal values Internally, each value of an enumerated type
is stored as an integer, called its ordinal value
The first value has an ordinal value of zero
The second one, and so on
You cannot assign a numeric value
to enumerated type, even if it corresponds to an ordinal value

9. Enumerated types: methods
The declaration of an enumerated type
is a special type of class
And each variable of that type is an object
methods associated with enumerated objects
The ordinal() method returns the numeric value
Of an enumerated type
The name() returns the name of the value
Refer to IceCream.java

10. Outline Creating Objects The String Class Packages Formatting Output
Enumerated Types
Wrapper Classes
Components and Containers
Images

11. Wrapper classes A wrapper class
is used to wrap a primitive value into an object
Ex: create an object that serves as a container to hold an int
represents a particular primitive type
Ex: Integer class represents a simple integer value
instantiated, stores a single primitive type value
Ex: Integer object store a single int value
its constructor accept the primitive value to store
Ex: Integer ageObj = new Integer (40);

12. Wrapper classes in the JAVA class library
For each primitive type in JAVA
There exists a corresponding wrapper class (java.lang)
Primitive type
Wrapper class
byte
Byte
short
Short
int
Integer
long
Long
float
Float
double
Double
char
Character
boolean
Boolean

13. Wrapper classes methods
manages the associated primitive type
Ex: Integer provides methods returning the int stored in it
Some methods of the Integer class
Integer (int value)
Constructor: creates an new Integer object storing value
float floatValue()
returns the value of this integer as the float type
static int parseInt (String str)
Returns the int corresponding to the value in str

14. Autoboxing/Unboxing Autoboxing is the automatic conversion between
Primitive value and corresponding wrapper object
Integer obj1;
int num1 = 69;
Obj1 = num1; // automatically creates an Integer object
Unboxing is the reverse condition
Integer obj2 = new Integer (69);
int num2;
num2 = Obj2; // automatically extracts the int value
Refer to wrapper_error.java

15. Using Dialog Boxes for Input/Output
Another way to gather input is to use a GUI
such as JOptionPane offered by Java
Which allows a programmer to use GUI for I/O
Making I/O more efficient and the program more attractive
JOptionPane
Contained in the package javax.swing
Offers two methods:
ShowInputDialog: allows user to input a string from keyboard
ShowMessageDialog: allows user to display results

16. Syntax for ShowInputDialog
To display a dialog box
Containing the string in the object stringExpression
Storing the input data in the String object str
The syntax to use the method is:
str = JOptionPane.showInputDialog(stringExpression);
A dialog appears on the screen
prompting user to enter data
Data is returned as a string and assigned to variable str
The user enters the data in the white area
Called text field

17. Syntax for showMessageDialog
The syntax to use showMessageDialog is
JoptionPane.showMessageDialog(null, messageStringExpression, boxTitleString, messageType).
messageStringExpression:evaluated and value appears in box
boxTitleString: the title of the dialog box
messageType: type of icon appearing in the dialog box
JoptionPane.ERROR_MESSAGE
JoptionPane.INFORMATION_MESSAGE
JoptionPane.Question_MESSAGE
JoptionPane.PLAIN_MESSAGE
JoptionPane.WARNING_MESSAGE