Monthly Archives: May 2020

OOD – Basic Elements of ADTs – Cryptography – Shannon

In.java

Basic elements of a data type.

API.
Class.
Access modifiers.
Instance variables.
Constructors.
Instance methods.
Variable names in methods.

Basic components that you need to understand to be able to build data types in Java.

NOTE:

You should be working on the programming assignment and gradient assignments before you start working on OOD programs.

Classwork/Homework: NO DUE DATE HAS BEEN ASSIGNED YET

These assignments are to be developed using the basic elements of data types.

Generating cryptograms. A cryptogram is obtained by scrambling English text by replacing each letter with another letter. Write a program, YI_Crypto1.java to generate a random permutation of the 26 letters and use this to map letters. Give example: Don’t scramble punctuation or whitespace.

crypto

Entropy. The Shannon entropy measures the information content of an input string and plays a cornerstone role in information theory and data compression.

Shannon Entropy Calculator

Shannon is famous for having founded information theory.
It was proposed by Claude Shannon in 1948, borrowing upon the concept in statistical thermodynamics. Assuming each character i appears with probability p(_{i}), the entropy is defined to be H = – sum p(_{i}) log(_{2})p(_{i}), where the contribution is 0 if p(_{i}) = 0. Compute entropy of DNA sequence.
(a) Write a program, YI_Entropy1.java to read in a ASCII text string from standard input, count the number of times each ASCII character occurs, and compute the entropy, assuming each character appears with the given probabilities.
(b) Repeat part (a) but use Unicode.

entropy1

OOD: BallDriver and CollidingBalls Videos

BallDriver Video #1
A short video for Ball and BallDriver – Looking at the geometry behind the relative distance between 2 balls.
Oops: I meant radius.

BallDriver Video #2
Going over the first changes we did to the original code.

BallDriver Video #3
Integrating the geometry into the implementation to have a better way to determine the distance apart from a pair of balls.

BallDriver Video #4
Overloading
A quick look at two constructors for the same class.

BallDriver Video #5
Ball ADT and BallDriver Complete
This is the final version of the BallDriver assignment. The important concept to learn is how accessor methods are used to get information from the input argument which is an object of the Ball ADT. This illustrates ENCAPSULATION since instance fields are private and public methods are needed to get access to their values.

BallDriver Video #6
Last video and final implementation (no color)

BallDriver Video #7
Code for color changing of the balls

BallDriver Video #8
Putting color in the BallDriver assignment.

CollidingBalls Video #9
Overloading Trick

How to make a short video of your animations using QuickTime

OOD: BlueJ – Stanford AI

February 26th, 2016

OOD: ADT Intro

January 30th, 2015

Start reading the material in this site:

Slides

The Math class:
Math.pow(10, 3)

In Java, numbers as primitive data types are not objects, so you can never invoke a method on a number.
Instead, you pass a number as an explicit parameter to a method
ClassName.methodName(parameters)
1. What happens to this code fragment when you compile it?

int x = 2;
System.out.println(x.pow(3));

2. What is the difference between an ADT and a primitive data type? What can you create with an ADT?

The String Class
In Java, strings are objects that belong to the class String.
You do not need to call a constructor to create a string object.

A string is a sequence of characters. Strings are objects of the String class.

The substring method computes substrings of a string.

The call s.substring(start, pastEnd)

returns a string that is made up of the characters in the string s, starting at position start, and containing all characters up to, but not including, the position pastEnd.

Here is an example:
String greeting = “Hello, World!”;
String sub = greeting.substring(0, 5); // sub is “Hello”

H e l l o , W o r l d !
0 1 2 3 4 5 6 7 8 9 10 11 12

The position number of the last character (12 for the string “Hello, World!”) is always 1 less than the length of the string.

Let us figure out how to extract the substring “World”.
Count characters starting at 0, not 1. You find that W, the eighth character, has position number 7. The first character that you don’t want, !, is the character at position 12 .

<—–5—->
H e l l o , |W o r l d | !
0 1 2 3 4 5 6 |7 8 9 10 11 | 12

String sub2 = greeting.substring(7, 12);

You can easily compute the length of the substring: It is pastEnd – start. For example, the string “World” has length 12 – 7 = 5.

If you omit the second parameter of the substring method, then all characters from the starting position to the end of the string are copied.

For example,
String tail = greeting.substring(7); // tail is “World!”

3. Why can you have multiple substring methods doing something different?

If you supply an illegal string position (a negative number, or a value that is larger than the length of the string), then your program terminates with an error message.

4. Will it be an error during compilation or at run time?

Strings and the char Type
Strings are sequences of Unicode characters.
Character literals look like string literals, but we use single quotes: ‘M’ is a character, “M” is a string containing a single character.

Characters have integer values.
ASCII link attached below

You can use escape sequences inside character literals. For example, ‘\n’ is the newline character, and ‘\u00E9’ is the character é.

“When Java was first designed, each Unicode character was encoded as a two-byte quantity. The char type was intended to hold the code of a Unicode character. However, as of 2003, Unicode had grown so large that some characters needed to be encoded as pairs of char values. Thus, you can no longer think of a char value as a character. Technically speaking, a char value is a code unit in the UTF-16 encoding of Unicode. That encoding represents the most common characters as a single char value, and less common or supplementary characters as a pair of char values.” Clay Horstmann
More on this in the stackoverflow link

The charAt method of the String class returns a code unit from a string. As with the substring method, the positions in the string are counted starting at 0.
For example, the statement

String greeting = “Hello”;
char ch = greeting.charAt(0);

sets ch to the value ‘H’.

5. How do you find out the number of characters a string has?
6. How can you create an array of char type containing all the characters of a string?

OOD: Chapter 2: VN 2.1 BlueJ

OOD Resources
BlueJ – Objects First

Chapter 2: VN 2.1 The naive ticket machine project

Chapter 2: VN 2.2 introduction to source code – fields and constructors

Chapter 2: VN 2.3 Creating, documenting and testing a new class

Chapter 3: VN 3.1 Fields of class types

Chapter 3: VN 3.2 Constructors and field initialization

Chapter 3: VN 3.3 Solving the 12-hour clock exercise

OOD – My School: Multi – ADT application And More

/**
 * Teacher t1 = new Teacher("Sarah", "Clark", 35, "female", "Hello, class!");
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class Teacher
{
    private String firstName;
    private String lastName;
    private String age;
    private String gender;
    private String greeting;
    private Course course;
    private Student aStudent;

    public Teacher(String firstName, String lastName,Course course,Student stu)
    {
        this.firstName = firstName;
        this.lastName = lastName;
        this.course = course;
        aStudent = stu;
    }

    // draw teacher(s)
    public void draw()
    {
        StdDraw.picture(-1,-1.5,"school_teachers.png",2,1);
    }
    
    // getter/accessor methods
    public String getName()
    {
        return firstName+ " " + lastName;
    }

    public String getAge()
    {
        return age;
    }    

    public String getGender()
    {
        return gender;
    }

    public String getGreeting()
    {
        return greeting;
    }

    public String toString()
    {
        String output = "";
        output += "Teacher name: " + firstName + " " + lastName + "\nCourse Taught: " + course + "\nStudent: " + aStudent ;

        return output;
    }
}

/**
 * Cistomized driver to test all the different parts of my class MySchoolTest
 *
 * @RA & mrs.e
 * @1.8 3/13/18 & 5/10/19
 */
public class MySchoolTest
{
    public static void main(String [] args)
    {
        //StdDraw.setXscale(-2.03,2.03);
        //StdDraw.setYscale(-2.03,2.03);
        StdDraw.setXscale(-2,2);
        StdDraw.setYscale(-2,2);
        
        //create an object of student
        //then create 3 objects of course
        //afterwards we add the 3 objects of course to the student 
        Student konoa = new Student("Konoa", "Smith", "15", "female", "1234");  
        konoa.draw();

        Course c1 = new Course("Biology", "5", "102");
        Course c2 = new Course("precalculus", "4", "136");
        Course c3 = new Course("APUSH", "7", "117");

        // create an object of Teacher
        Teacher mrBill = new Teacher("Jasmine", "Flores", "28", "MYOB", "Namaste", c1);
        // print a teacher
        System.out.println("\n" + mrBill);
        mrBill.draw();

        // print a course information
        System.out.println("Print a course ");
        System.out.println(c1);

        // add all courses to an array
        Course [] courses = { c1,c2,c3};

        // assign all courses to a student
        konoa.setCourses(courses);
        c1.draw();
        //print a student info and courses
        System.out.println("\n" + konoa);
        
        /**
        *  I omitted the school object for easier understanding 
        *  of few interacting ADT objects
        */
    }

}

/* 
 * Teacher name: Jasmine Flores
 * Course Taught: 
 * Class name: Biology
 * Room Number: 102
 * Period:  5
 * 
 * Print a course 
 * Class name: Biology
 * Room Number: 102
 * Period:  5

 * Student name: Konoa Smith
 * Courses: 

 * Class name: Biology
 * Room Number: 102
 * Period:  5

 * Class name: precalculus
 * Room Number: 136
 * Period:  4

 * Class name: APUSH
 * Room Number: 117
 * Period:  7

 * 
 */

Mrs. Elias's Intro to Computers (Acc)

Class Website at PHS