One class can describe many different instances

1
Maria
Hello
Rumi
Rumi says Hello
Maria says Hello

• One class can describe many different instances
• Two NameDroppers, each with their own myName
  field
• In Java, the transform method for NameDropper is
• this.myName means this instances myName
  field

String transform(String thePhrase) return
this.myName " says " thePhrase
2
Fields and Constructors

• A NameDropper must know its name from the very
  beginning
• We use a constructor to set the field called
  myName
• Then, when we invoke NameDroppers constructor,
  we give it an argument

NameDropper(String whatMyNameIs)
this.myName whatMyNameIs
new NameDropper("Rumi") new NameDropper("Maria")
3
ClassFields, Constructors, Methods

• public class NameDropper extends
  StringTransformer
  implements StringTransformable
• private String name // field persistent
  storage, a permanent part
  // of each
  NameDropper
• public NameDropper(String whatMyNameIs) //
  Constructor
• this.name whatMyNameIs
• public String transform(String whatToSay) //
  Method
• return this.name " says " whatToSay

Questions?
Private means private to the class. The standard
is that fields are generally private and all else
is public (for now) more on this later.