Todays Work Hw3

1
Todays Work (Hw3 1)

• Read Note on textbook 40
• Floating-point numbers are stored
  approximately(Example)System.out.println( 1 -
  0.1 -0.1 - 0.1 - 0.1 - 0.1 )gt
  0.5000000000000001 (Not 0.5)System.out.println(
  1.0 - 0.9 )gt 0.09999999999999998 (Not 0.1)
• Integer numbers are stored precisely
• Calculation with integers yield a precise
  integer result

• Read caution on Page 42
• Division of two integers yields an integer in
  Java.
• (Example)( 5/9) gt 0( 5.0 / 9 ) gt
  0.5555555555555556
• Cast operator
• double re
• re ((double)5/9)

2
Todays Work ( 2)

• Converting positive decimal integer to binary
• (Example) See Page 11
• Use mod () operator to get remainder
• 9 gt 9/2 4 gt 92 1
• 4/2 gt 2 gt 42 0
• 2/2 gt 1 gt 22 0
• 1001 ( 1 23 ) ( 0 22 ) ( 0 21)
  (1 20) 9
• Use while loop and repeated division by 2
• Use string concatenation () to prepend each new
  remainder
• String a 001"
• String b 1a ba gt a 1001"

3
Todays Work ( 3)

• Reads four hexadecimal digits and displays the
  corresponding Unicode character in a JOptionPane.
  
• Example
• entering 0041 will display A
• entering 0067 will display g
• Use parseInt(String s, int radix)to get decimal
  value
• Convert this decimal value to character
• iInteger.parseInt("0041",16)
• System.out.println((char)i)

4
Todays Work (3)

• Check if the input is 4-digit number
• use String.length() method
• if (hexstring.length() 4)
• Check if input is hexadecimal digit
• try
• i Integer.parseInt (hexstring, 16)
• catch (Exception ex)
• System.out.println( This is not
  hexadecimal value")

5
Todays Work (4)

• Make True table like Table 2.8,2.9,2.10 (page 48,
  49)
• --------------------------------------------------
  --
• p1 p2 p1p2
• --------------------------------------------------
  -
• False false false
• false true false
• true false false
• true true true
• Use a static method
• For (int p1int 0 p1int lt 1 p1int)
• p1 intToBoolean(p1int)