Character Encoding

1
Character Encoding Handling doubles

• Pepper

2
Character encoding schemes

• EBCDIC older with jumps in alphabet
• ASCII 1967 (7 bit) Handled English,
• ASCII extended (8 bit) handled special
  characters such as ñ and
• UNICODE (16 bits) all language not Klingon,
  Egyption hieroglyphics (sometimes uses fewer bits)

3
Print Unicode table

• Create a for loop to run 340 times
• Convert count to char with a cast
• char x (char) count
• Print "When the number is " count " the
  character is " x
• Be sure to set unlimited buffering on your BlueJ
  window.

4
character printing code

• public class characters
• public static void main()
• for (int count 1 count lt 500 count)
• char x (char) count
• System.out.println("When the number is " count
  " the character is " x)

5
Doubles not exact

• Stored binary, so .41 is actually a repeating
  sequence starting with .01101000111101011100001010
  001111
• http//www.mathsisfun.com/binary-decimal-hexadecim
  al-converter.html
• To explain how decimal portions convert
• http//www.mathsisfun.com/base-conversion-method.h
  tml

6
Converting 41/100 to binary
Place Equation Result
1 Note decimal .
2 .412 .82 0
3 .822 1.64 1
4 .642 1.28 1
5 .282 .56 0
Result a repeating pattern of
.01101000111101011100001010001111
7
doubles check equal

• small differences mean little errors creep in.
• Math.abs(dollars1 - dollars2) lt .001
• ex Write a program to Multiply .41 .41 and
  compare it to .1681
• print the values so you see the diff
• try an comparison to see it fail
• try the test for no more than .001 off

8
double check equal

• public class testdouble
• public static void main()
• double x .41.41
• double y .1681
• System.out.println("x is " x " and y
  is " y)
• if (x y)
• System.out.println("match with equal
  sign")
• else
• System.out.println("no match with
  equal sign")
• if (Math.abs(x-y)lt .001)
• System.out.println("match")

9
printing double

• System.out.printf("x is .2f ", x)
• OR
• import java.text.DecimalFormat
• DecimalFormat twoDec new DecimalFormat("0.00")
• System.out.println("x is " twoDec.format(x))

10
More on Decimal Formatter

• DecimalFormatter object knows How to print
  decimals
• Package to import import java.text.DecimalFormat
  
• How to create a DecimalFormatter for your
  numbers
• DecimalFormat percentage2 new
  DecimalFormat(0.00)
• How to use a DecimalFormatter to print to your
  screen
• System.out.println(percentage2.format(.308)) //
  will print 30.80
• Different format options
• 0 required position
• show it if you have it
• make it a (mult by 100)
• E E notation (scientific)
• Now you change your program to print x with only
  2 decimal places

11
Printf

• printf command
• Just like println, but uses variables inside
  string start and end character.
• , then size of whole number, then decimal places
  and then type
• d int
• f float
• s string
• c char