getFamilyName(%20)%20with%20one%20"name"%20field

1
getFamilyName( ) with one "name" field

• We will assume these specifications for the
  "name" field
• The name field consists of these parts, in this
  order
• 1) the family name, possibly including some
  (single) blank characters
• 2) a double blank " " if necessary to separate
  the family name from the
• given names.
• 3) zero or more given names
• 4) maybe some trailing blanks
• At least part (1) is required, but the field may
  omit later parts.
• (Or "Parts 1 to N are required, where N gt 1. If
  part k is omitted, all
• parts j must be omitted, with j gt k. Or ?)
• Examples
• name CLARKE JIM family name CLARKE
• CLA R JIM CLA R
• CLA CLA
• CLAb CLA
• bb "" (empty string)

2
Keep it simple on the first try

• int pos 0 // the current character position
• String result "" // the family name
• // that we're building up
• 1. while (pos lt name.length())
• 2. if (name.charAt(pos) ' ')
• 3. if (name.charAt(pos1) ' ') // not ""
• 4. return result
• 5.
• 6. else
• 7. result name.charAt(pos)
• 8. pos // pos pos 1
• 9.
• What about "CLAbR"?
• What about "CLA"?
• What about "CLAb"?

3
Fixed, we hope

• public String getFamilyName ()
• int pos 0 // the current character position
• String result "" // the family name
• // that we're building up
• while (pos lt name.length())
• if (name.charAt(pos) ' ')
• if (pos 1 name.length()
• name.charAt(pos1) ' ')
• return result
• result name.charAt(pos)
• pos
• return result

4
A common loop pattern

• int pos 0
• ...
• while (pos lt name.length())
• ...
• pos
• This is an example of a very common pattern
• INITIALIZE
• while (TEST WHETHER TO DO ANOTHER CYCLE)
• body
• STEP TO PREPARE FOR ANOTHER CYCLE
• So we have a special statement, a "for" loop
• for (INITIALIZE TEST STEP)
• body

5
Our loop, rewritten

• public String getFamilyName ()
• String result "" // the family name
• // that we're building up
• for (int pos 0 pos lt name.length() pos)
  
• if (name.charAt(pos) ' ')
• ((pos 1 name.length()
• name.charAt(pos1) ' '))
• return result
• result name.charAt(pos)
• return result

6
Using String methods

• 1) indexOf
• To find the first double blank, we can just
  say
• int where name.indexOf(" ")
• Then, if there was no double blank, we can
  make the result be almost
• the same as name, and otherwise we just use
  the first part
• if (where -1)
• // return the same as name, except for a
• // possible final blank
• else
• // return the part of name from position
• // 0 to position where-1
• 2) substring
• To find the part of the name from 0 to
  where1, we can say
• name.substring(0, where)

7
Rewritten again

• public String getFamilyName ()
• int where name.indexOf(" ")
• if (where -1)
• //return name --what about final blank?
• return name.trim()
• else
• return name.substring(0, where)

8
How the Student class handles names

• class Student
• private String name
• public Student (String theName, ...) ...
• public void setName (String newName) ...
• public String getName () return name
• public String getFamilyName ()
• ... // a LOT of stuff, and hard work too
• class TestStu public static void main (...)
• // Here we create many Students and carry out
  many operations on
• // names. How often do we separate a name into
  its parts?

9
Redesigning the Student class

• class Student
• private String familyName
• private String givenNames
• public Student (String theName, ...) ...
• public void setName (String newName) ...
• public String getName ()
• return familyName " " givenNames
• public String getFamilyName ()
• return familyName
• private void breakUpName (String name) ...

10
A private method

• class Student
• private String familyName
• private String givenNames
• private void breakUpName (String name)
• int where name.indexOf(" ")
• if (where -1)
• familyName name.trim()
• givenNames ""
• else
• familyName name.substring(0, where)
• givenNames name.substring(where 2)
• ...

11
Using the new method

• class Student
• private String familyName
• private String givenNames
• private void breakUpName (String name) ...
• public Student (String theName, ...)
• breakUpName(theName)
• ...
• public void setName (String newName)
• breakUpName(newName)

12
An exercise

• class Student
• private int numCourses // including failures
• private int numPassed
• private double avgMark // including failures
• public static final int PASS_MARK 50
• // includeNewMarkInAvg update the records to
• // include a new course mark.
• public ??? includeNewMarkInAvg (??? mark)
• ???
• Exercise replace the ???s with Java code. Write
  part of a main( ) method to use the new Student
  class.