Essential Question: How does an algorithm compare to a mathematical model in physics or engineering?

5. Correctly use recursion. Read the Barron's book write up on recursion. Click here for a simple example of recursion. Relevance: If you can do recursions you can learn to do anything in Comp Sci.
   • Must call itself within the method
   • Must alter one or more of its arguments each time it calls itself.

   • Must have a means of stopping itself based on the modified argument(s)

   • Stores calculated values in a stack and evaluates them after the recursion stops. uses last-in-first-out (LIFO).

6. Determine the number of iterations a given recursion will have.

1. Correctly use the three forms of comments:

• // Single line comment

• /* One or more lines of comments*/

• /** Javadoc comments*/

2. Identify reserved words (p. 107).

3. Distinguish between syntax and style.

syntax: is the defined form the source code must have. Improper syntax will prevent a program from compiling.

style: is the recognized form source code should take to be easily read and understood by other programmers. Improper form wil not prevent a program from compiling.

2. Correctly use the naming conventions for classes, methods, and fields.

• Capitalize the first letter of classes and constructors but not libraries, packages, methods, fields, or variables.

• The first character must be a letter & have no spaces in it.

• Names can include letters, numbers or the underscore_.

• Names should be descriptive.

• Method names = verbs, field = nouns

• Symbolic constants use all capitals. example: Math.PI , PI is a public symbolic constant that's a field in the Math class.

4. Correctly indent programs. All code that belongs inside a set of curly brackets should be indented. Henceforth, deductions will be made for improper indentation. Correct indentation is a style issue.

example:

public class stuff {

        public static void main ( ) {

                for ( int x = 0 ; x < 12 ; x++ ) {

                        if ( x == 12 ) {

                                // some code

                                                  }

                }

        }

}

Homefun (summative/formative assessment):

Read Chap. 5; Princeton professor foresees computer science revolution

Exercises 3, 4, 5, 7, 8, 10

 

Programming Assignment: Lab 5.6

 

Relevance: A program won't run without proper syntax. Proper style makes the code readable so that it can be modified and maintained.

 

Essential Question: How is an expression in a programming language different from the same expression in algebra?

5. Understand the meaning and use of the equal sign in Java.

• Can have only one field or variable on the left side

• Means "replaced by", not equals

6. Correctly declare fields, class variables, and local variables or instances.

• Fields: Declared inside a class but NOT inside a method. CANNOT be static

• Class Variables: Declared inside a class but NOT inside a method. MUST be static.

• Local Variables or instances : Declared inside a method.

6. Correctly initialize (set starting values for) fields, class variables, and local variables or instances.

• Fields and class variables: Usually initialized by constructors.

• Local variables or instances: Can only be initialized locally

6. State the default values used for initializing fields or class variables. Note that these are created inside of a class but not inside of a method.

• Numeric types: 0

• Objects or instances: null

9. State the default value used for initializing local variables. (Local variable are created inside of methods. There is no default value for local variables.)

10. State the eight types of primitive data types and their sizes in bytes. (p. 129)

Data Type	Size (Bytes)	Values
boolean	1	true or false
char	2	Unicode characters
byte	1	very short integer
short	2	short integer
int	4	integer
long	8	large sized integer
float	4	floating point (number with decimal)
double	8	larger floating point

9. Explain why the largest size of an integer or long variable can be a major issue. The size is finite and if the size is exceeded the program will not work.

Data Type	Max size
int	from  - 2.1 x 10 9     to   2.1 x 10 9 -1
long	from  - 9.2  x 10 18   to   9.2  x 10 18 -1
float	from  - 3.4  x 10 38    to   3.4 x 10 38
double	from  - 1.8  x 10 308   to  1.8 x 10 308

9. Explain the limitations of precision on floating point data types (float or double) and why these limitations can produce round-off errors. Byte, short, integer, or long have size limitations but are exact numbers, On the other hand, floating point numbers are often not exact. They have a limited number of significant figures, which can be less than the number of decimal places. For example: a number as large as 1.8 x 10 ³⁰⁸ would not have 308 significant figures.

Repetitive calculations can produce significant rounding errors. Click here for an example of code that produces significant rounding errors.

9. State the primitive data types which do not have a true zero and explain why this can be a problem. double and float. These are stored as base 2 logarithms and there is no logarithm for zero.

10. Correctly Use:

• literal constant - letters in single quotes and numbers.

examples: 'a', 2, 37.5, 'D', 42.005

• symbolic constant - declared and initialized using final.

example: final int XXX = 5;

• escape sequences (used when outputting Strings. See p.131)

examples of escape sequences
escape sequence	effect
\n	creates a new line
\t	creates a tab
\\	outputs \
\"	outputs "

code example: System.out.print ( "Using \"escape sequences\"  \n is fun!" ) ;

 

 Scope

15. Understand the term scope (p. 133). Note: the concept of scope is incredibly important to programming in Java. You must consider it whenever you create a variable. As a matter of style, variables should be declared at the top limit of their scope. Click here for an example of scope.

• inside the { } of a class

• inside the { } of a method

• inside the { } of a loop, if, else statement, or any other set of {}

16. Correctly convert numbers and objects into strings and explain why objects need special attention. (An object may have multiple variables or fields of different data types associated with them, hence the output has to be defined in order to understand how it should be done.)

• Concatenate to an empty string. Example: System.out.print ("" + 6);

• Use toString method for converting objects to strings By default, the toString method outputs an object's class name and memory location. To output something more meaningful the method has to be overridden or in other words, redefined in the object's class (see toStringDemo at right).

Homefun (summative/formative assessment): read Sections 6.1 to 6.5; Exercises 1- 7 p.146-147

 

Essential Question: Is 1/2 the same thing as 1.0 / 2.0?

Integer Math, Autoboxing and Type Casting

17. Use literal constants as either int or doubles (Example: int: 2, double: 2.0).

18. Correctly use the order of operation for arithmetic.

    1. parentheses

    2. division, multiplication, modulus

    3. addition, subtraction

19. Perform division using integers and doubles.

Integer division truncates the decimal portion of a number. It does NOT round numbers. Mixed division of integers and doubles upgrades the answer to a double (this is called autoboxing).

Examples:

division of integers: 1 / 2       yields 0

division of doubles: 1.0 / 2.0 yields 0.5

mixed division:         1 / 2.0    yields 0.5,  1.0 / 2 yields 0.5  

 

Depending on autoboxing can cause unexpected problems due to order of operation. If you don't want to truncate decimals and do want a double then use double literal constants!

Examples:

int & double literal constants: 1 / 2 * 2.0        yields 0

                                                                             1.0 / 2 * 2        yields 1.0

                                                                             1 / 2.0 * 2        yields 1.0

only double literal constants:  1.0 / 2.0 * 2.0  yields 1.0

20. Cast variables. This temporarily changes the data type of a variable.

    Example:

    int a = 2, b = 5;

    double c;

    c = ( double ) a / b ; // c has a value of 0.4 . The variable a is temporarily

    // type cast as a double causing b to be autoboxed as a double.

     

    c = a / b ; // c now has a value of 0.0 . Although a was type cast as a

    // double, it returns to being an integer if no longer type cast.

    c = ( double ) ( a / b ) ; // c has a value of 0.0 . Due to order of operation,

    // a/b occurs before the type casting to double.

     

21. Truncate and round numbers using integer division.

Examples:

Normal Rounding:

0.5 rounded to nearest whole number

roundedValue = ( (int) ( 0.5*10 ) + 5 ) / 10 ; // yields 1

 

x  rounded to nearest whole number

roundedValue = ( (int) ( x*10 ) + 5 ) / 10 ; // assumes x & y are int

Rounding Upward--When billing customers, rounding tenths of cents upward can result in millions of dollars of extra profit.

0.1 rounds tenths upward to nearest whole number

roundedValue = ( ( int ) ( 1*10 ) + 9 ) / 10 ; // yields 1

 

x  rounds tenths upward to nearest whole number

roundedValue = ( ( int ) ( x * 10 ) + 9 ) / 10 ; // assumes x & y are int

Rounding downward--When paying debts, rounding tenths of cents downward can result in millions of dollars of extra profit.

0.9 rounds all decimal places downward (truncates)

roundedValue =  (int) (0.9 * 10 ) / 10 ; // yields 0

 

x  rounded to nearest whole number

roundedValue =  (int) ( x * 10 ) / 10 ; // assumes x & y are int

Relevance: Handling massive numbers of transactions involving money without losing any funds due to rounding errors is a major issue for international finance and businesses.

22. Perform math with characters.

Characters are stored as integers and can be used to perform integer math. (See example code.)

summative/formative assessment (in class): Create 10 practice problems using integer math, order of operation and type casting. Trade with a partner and work the practice problems on paper. Run the code and check your answers.

Essential Question: Why did you learn to find remainders in grade school instead of going straight to long division ? Modulus Math
Correctly use various arithmetic operators including: modulus (%) returns remainder: 1 = 5 % 2 compound         assignment operators (/=, +=, -=, *=, %=) increment/decrement (y++, ++y, y--, --y)	Modulus Examples 1 = 1 % 3 2 = 2 % 3 0 = 3 % 3 1 = 4 % 3 2 = 5 % 3 0 = 6 % 3

example:

int offSwitch, x, offPoint = 5 ;

offSwitch = ( x % offPoint ) / x ; // Try evaluating this code for values

                                                // of x from 1 to 10

Homefun (summative/formative assessment): Read Sections 6.6 to 6.10; Exercises 4, 6, 8, 10, 11, 12 p.147-148, Click here. Work the practice problems on paper and then run the code.

 

 

Programming Assignment: Lab 6.10 and Exercise 13 (write a program) p.148

Programming Assignment--Shapes Program: Write a program which uses command line input to input a single dimension in centimeters. Use this dimension to calculate and output the surface area and volume of a cube, sphere, and cylinder along with the correct units. The radius and height of the cylinder are equal to the dimension that was input. Use a separate method for each calculation.

 

Essential Question: How does a progressive income tax system work and is it a good idea?

Note: with a progressive income tax, when a higher rate is triggered the taxpayer only pays the higher rate on income above the amount that triggers the higher rate.

Tax code program: Modify the code provided so that it meets the following specifications:

Input: income in dollars.

Output:

• Taxable income in dollars (show only 2 decimal places).

• Tax due in dollars (round tenths of cents upward and show only 2 decimal places).

• Nominal tax rate in % of income (show only 1 decimal places).

NTR = (taxDue) / (income) *100

Description: The program will round any tenths of a cent upward. "If" statements are not allowed. The program will use only algorithms to calculate taxes. It will use the following progressive tax table:

 

Income ($)	Tax Rate	Comments
0 to 19,999.99	00 %	This part of income is never taxed
20,000 to 29,999.99	25 %	Only income above $19,999.99 is taxed at 25%
30,000 +	35 %	Only Income above $29,999.99 is taxed at 35%. Note this is an additional 10% above the 25% tax that kicks in at $29,999.99.

 

Homefun (summative/formative assessment):

Practice Test

Summative Assessment: Test Chap 5 & 6 Objectives 1-24

1. Recognize literal strings. characters enclosed in double quotes, example: "This is a literal string"
2. Be familiar with the 2 most common of String's 9 constructors.

• String ( )
• String ( String s )

3. Be aware that Strings are immutable objects.
4. Understand how Strings are initialized.

• String s1 = " ";                   // s1 is set to an empty String
• String s2 = new String();    // s2 is set to an empty String
• String s3;                           // s3 is set to null

5. Be aware that calling a String method with a String set to null will give run-time errors. (An empty string initialized to " " is not the same thing as a string initialized to null.)
6. Correctly use common String methods (See table on p. 265.)

• length ( )
• charAt ( pos )    // Note that characters are counted starting at 0.
• substring ( pos )
• substring ( fromPos, toPos )
• compareTo ( s2 )  // returns neg int if s1 <s2, 0 if s1 = s2, pos int if s1>s2
• compareToIgnoreCase ( s2 )   //returns neg int if s1 <s2, 0 if s1 = s2, pos int if s1>s2 ignoring case
• equals( s2 )   // returns a boolean true or false
• equalsIgnoreCase ( s2 )  // returns a boolean true or false ignoring case
• indexOf ( ch )   // four types
• lastIndexOf ( ch )   // four types
• trim ( )   // removes white space characters from beginning and end of string
• replace ( oldChar, newChar )
• toUpperCase ( )
• toLowerCase ( )

See example code VowelFinder

7. Correctly use the various ways of doing concatenation (adding Strings). (p. 266)

• yourString += str;
• yourString = yourString1 + str;
• yourString.concat (str);

8. Correctly use relational operators with Strings. p. 268)
9. CANNOT use == , != , < , >, <= , >=
10. CAN use: (Note that a string instance must call the method and a second string must be entered as and argument to compare the 2 strings.)

s1.equals ( s2 )                          

s1.equalsIgnoreCase ( s2 )       

s1.compareTo ( s2 ) methods

s1.compareToIgnoreCase ( s2 )

11. Correctly convert numbers into Strings and Strings into numbers.

examples:

int yourInteger = Integer.parseInt ( yourString ) ;     

String yourString = String.valueOf ( yourNumber ) ;

 

13. Correctly use the Character wrapper class methods. (sample code, also see p.275)

14. Correctly use the StringBuffer class (p. 278).

Homefun (summative/formative assessment):

1. Exercises 1-6
2. Examine and run the compareToDemo program and write a short description of what the compareTo method returns. On the next test, given two strings s1 and s2, you should be able to state the exact number returned by s1.compareTo (s2). (Assume that you have an ASCII table.)
3. Modify the above code to run with compareToIgnoreCase and write a short description of what the compareTognoreCase method returns. On the next test, given two strings s1 and s2, you should be able to state the exact number returned by s1.compareTognoreCase (s2). (Assume that you have an ASCII table.)

 

Programming assignments (summative/formative assessment):

1. Write a program that:

• inputs 2 strings using command line input.
• Output the length of both strings, the 3rd character in both strings.
• Test the strings to see if they are the same and output whether they are. Concatenate the two strings and output the result.
• Output any capital letters in the concatenated string along with their position.

3. Write a program that inputs a string using command line input and tests it to determine if it's a palindrome.
4. Write a a program that inputs 3 strings using command line input and outputs them in alphabetical order.

Summative Assessment: Test Chap 10 Objectives 1-13

Chap. 12 Arrays and ArrayLists

1. Correctly declare and initialize arrays.

• int scores [ ] = new int [5] ;
• int scores [ ] =  { 93, 67, 99, 87, 91 } ;

2. State the default values when initializing arrays

• numbers = 0
• boolean = false
• objects = null

3. Know that once declared and initialized, the size of an array cannot be changed.
4. Know that the elements of arrays are numbered starting with 0. These elements can be randomly accessed using the indices or subscripts.
5. Correctly use the array length field. example: array.length, note that strings use length ( )
6. Be aware that arrays are always passed to methods by reference. When an object is passed by reference, the memory address of the starting point of the array is passed into the method. Any work done on the array by the method continues to exist after the method finishes running. It's not necessary to return an array to get values out of a method.

given : int incomes [ ] = new int [ 5 ] ;

example of a method's parameters : someMethod ( int inc [ ] ) ;

example of calling the method : someMethod ( incomes ) ;

Note: the [ ] in the example indicates that an array is being passed to the method. Do not put the size of the array in the brackets. Do not use the [ ] when using an array as an argument. (See example code.)

7. Correctly declare and initialize 2D arrays.

final int ROWS = 2;

final int COLS = 3;

double name2DArray [ ] [ ] = new double [ROWS] [COLS] ;

    or

double name2DArray [ ] [ ] =

{

        {0.0, 2.7, 5.6},

        {4.3, 1.4, 7.2}

};

8. Be aware that the first dimension in a two dimension array is considered the number of rows while the second dimension is the number of columns.
9. Correctly use the length field to  find the number of rows and columns.

• twoDArray.length returns the number of rows
• twoDArray[0].length returns the number of columns

10. Be aware that arrays with more than 2 dimensions can be declared.
11. Correctly use parallel arrays.
12. Correctly use ArrayList. example code
13. State the advantage of using ArrayList. Can expand and contract as needed
14. Be familiar with ArrayList's constructors and methods (see page 331).
15. Be aware of the pitfalls of using ArrayLists. They can only store objects or instances and require more memory than arrays. Manipulating data in an arrayList generally requires more processing time than in an array, but this is usually not a significant problem with up to date computer hardware.
16. Describe how classes and arrays are key elements used to form data structures.
17. Describe why abstraction is an important theme in data structures.
18. Be as one with Chapter 2 of GridWorld.

 

Homefun: Exercises 1-5;

Programming assignments: Lab 12.9, 12.11

 

12.1 Simple Data Base Program

Create a program with a class called Employees. In the main method create 3 parallel ArrayLists: 2 holding 6 first names and 6 last names plus a third ArrayList with the corresponding Salary for each employee. Use an output method concatenate the first and last names, and output the data in two columns as shown in the example:

 

Name                 Salary $1000/yr

Bob Arnold            90

Herb Bobo            12

Jane Cool             27

Alfred Nameless   49

Juan  Smith          200

Betty Taylor         142

Next, output the total of all salaries. Use a random number generator to fire two employees. Remove them from the Array List then add a new employee called Bob Newguy with a salary of $200,000. Again, output a table with the names of the current employees and their salaries. Also output the total of all salaries.

12.2 2-D Array Output

Create a program with a class called Alphabet with 3 local (inside main method) of 2-dimentional arrays: each will contain a large-sized letter respectively A, B, and C. Use a separate method to output the letters alphabetically in a column with A at the top.

Note: You need to write the letters on graph paper or in an Excel spread sheet in order to understand how many spaces are needed. To understand how the arrays should be initialized look at chapter 10 objective 7 above. You do not need to reproduce the grid lines in your program's output.

      

	0	1	2	3	4	5	6	7	8	9	10
0						A
1					A		A
2				A				A
3			A	A	A	A	A	A	A
4		A								A
5	A										A

     

 

GridWorld: Read Chapter 2, Exercises 1-4

Summative Assessment: Test Chap 12 Objectives 1-16