Primitives in Java

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Primitives in Java

• Characters char a, b 16 bits 2 bytes
• Smallest integers byte -128 to 127 8 bits 1
  byte
• Small integers short -32768 to 32767 16 bits
  2 bytes
• Integers int -2147483648 to 32 bits 4 bytes
• 2147483647
• Big integer long -9223372036854775808 to 64
  bits 8 bytes
• 9223372036854775807
• Decimals float -1.45E-45 to -3.4E38 32 bits
  4 bytes
• Big decimals double -4.9E-324 to -1.79E308 64
  bits 8 bytes
• Boolean boolean true or false 1 bit
• Emptyness void - 0 bit

AAAAARGH !!!
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The ones we will use

• int integers
• float decimals
• double big decimals
• boolean true or false
• void emptyness
• char characters

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Example 1, using an integer

• public class FirstTry
• public static void main(String args)
• System.out.println("Hello dude!!!")
• int someNumber
• someNumber 18
• System.out.println("I just turned "
  someNumber)

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Example 1, result
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Example 2

• public class FirstTry
• public static void main(String args)
• System.out.println("Hello dude!!!")
• int someNumber
• double someDecimal
• char myEffortRating
• someNumber 18
• someDecimal 166.85
• myEffortRating B
• System.out.println("I just turned "
  someNumber)
• System.out.println(My height is "
  someDecimal " cm")
• System.out.println(My effort rating is "
  myEffortRating)

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Example 2, result
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Our first real program

• Pseudo Code
• Input n
• Sum ? 0
• i ? 1
• Repeat the following 3 steps
• while i lt n
• Sq i i
• Sum ? Sum Sq
• i ? i 1
• Output Sum

• Actual Code
• public class SumOfSq
• public static void main(String args)
• int n, sum, i, sq
• sum 0
• i 1
• n 100
• while (i lt n)
• sq i i
• sum sum sq
• i i 1
• System.out.println("the sum of the " n "
  first squares is "sum)

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Result
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Some Java rules

• Put a after each statement but not after a
• // is used for comments, these statements will
  not be considered by the compiler. These will
  appear in green
• / / is for a bloc of comments
• Things you want executed should be in
• public static void main(String args)
• You must declare all variables and give them a
  type Ex int n
• You can declare many variables of the same type
  in one line Ex int n, sum, i, sq

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First Assignment

• Write a pseudo code as a Word Doc before writing
  your actual program
• Write a Java program called InterestCalc
• Write comments in a bloc stating your name, etc
  Ex
• /
• Assignment 1
• Form 7, AP Java
• Author Joe Scablowsky
• version 1.00 04/09/09
• /
• The program should add a 10 interest a year on
  an initial amount of 5000 and this for 20 years.
• Display the result on the console using
  System.out

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Hints

• After the first year, you could calculate your
  interests like this
• amount amount amount 0.1
• You will need to some doubles (decimals)
  Ex. for amount
• You will need to use a while loop
• For the while loop, see book p 298

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Result

• The result should look like this

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