Computer Science 111 Fundamentals of Computer Programming I

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Computer Science 111Fundamentals of Computer
Programming I

• Char, Stringsand Menu DrivenTerminal I/O

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Repeating Input

• Want program to allow user to continue giving
  inputs as long as there are more problems of the
  same type he/she wishes to solve.
• For example, convert several temperatures without
  having to run the program over and over.

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Repeating Input (cont.)

• Common structure goAgain y while
  goAgain y get input calculate
  and give results read goAgain

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Repeating Input (cont.)

• Often we want user to enter a letter (y or n)
  rather than a number.
• There is type char for variables that store a
  single character.
• Literals of type char are written in single
  quotes (apostrophes).

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Repeating Input (cont.)

• char goAgaingoAgain ywhile (goAgain
  y) fahrenheit reader.readDouble(Ente
  r fahrenheit ) celsius
  (fahrenheit-32.0) 5.0 / 9.0
  writer.print (Celsius is )
  writer.println(celsius) goAgain
  reader.readChar(More input (y or n)? )

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Strings

• Java also has a type called String. A string is
  an object (not primitive data type like int). A
  variable of type String holds a reference to a
  string object (a sequence of 0 or more
  characters).
• Literals of type string are contained in double
  quotes.
• When we do writer.print(Enter a Fahrenheit
  number )we are using a string literal
• We could have String prompt prompt
  Enter a Fahrenheit number
  writer.print(prompt)

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String Concatenation

• When dealing with strings, the operator
  provides string concatenation. For example,
  Today is Wednesday. results in the string
  Today isWednesday.
• If a string is concatenated with another data
  type, the other type is first converted to its
  string format.

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Concatenation Examples

• Total pay is 6 40 results in Total pay
  is 240
• Total hours is 30 15 results inTotal
  hours is 3015
• Total hours is (30 15) results inTotal
  hours is 45
• Note we can now do things likewriter.println(Th
  e quotient of dividend divided
  by divisor is
  dividend/divisor .)

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Newline Characters

• You can add the character \n to a string to
  cause the string to break to a new line.
• For example, writer.println(Now is the time
  \nfor all good men \nto come to the aid \n
  of their country.) results in Now
  is the time for all good men to
  come to the aid of their country.

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String Input

• The KeyboardReader class has a method called
  readLine that reads everything the user enters up
  to but not including the Enter key.
• Example String dayOfWeek
  writer.print(Enter the day of the week )
  dayOfWeek reader.readLine()

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A Menu Driven Terminal I/O Program

• Program should allow user to continually choose
  between options of
• printing the first n Fibonacci numbers
• printing the primes less than or equal to n
• Quitting
• Solution is an in-class example. Also in class
  folder.

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Math Class
Method/Constant Explanation double
abs(double) returns absolute value also
for float,int,longdouble exp(double) returns e
to power of parameterdouble log(double) returns
logarithm base edouble max(double,double) returns
max of two, also for float, int,long. Also
a min method.double pow(double,double) returns
first param raised to seconddouble
random() returns random num, 0.0ltnumlt 1.0long
round(double) returns nearest longdouble
sin(double) returns trig sine in radians
also cos, tandouble sqrt(double) returns square
rootdouble E double closest to edouble
PI double closest to ?
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Programming Style

• Use comments
• Give a header to program with programmers name,
  date, course, purpose of the program, special
  assumptions, known bugs, etc.
• Give use of variables, if not perfectly clear.
• Describe sections of program
• Explain any code that may not be clear.

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Programming Style (cont.)

• Indentation and braces
• methods public void run( )
  code indented
  code indented
• if if (cond)
  code indented
  code indented
  else
  code indented
  code indented
• while Same as if

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Programming Style (cont.)

• Names
• Use meaningful names
• Variables and methods use camelCase
• Classes start with upper case.

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Man, there must be 1100110001001001100 cows out
there!