Lecture Notes

CSE 142

Week 1 Wednesday Lecture

About CSE 142

• Learning Objectives
  • Functionality/Behavior - write functionally correct Java programs that meet a provided specification and/or solve a specified problem.
  • Functional Decomposition - break down problems into subproblems that are modular and reusable, and define methods to represent those subproblems.
  • Control Structures - select and apply control structures (e.g. methods, loops, conditionals) to manage the flow of control and information in programs.
  • Data Abstraction - select and apply basic data abstractions to manage and manipulate data in programs.
  • Code Quality - define programs that are well-written, readable, maintainable, and conform to established standards.
• 1/5 is about if the code works - it is not enough for the code to work. Code is for people, not computers. Code must be readable, well-written, and maintainable.

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Course Components

• Lessons on MWF 11:30 in KNE; recordings will be released afterwards. First introduction to course concepts. Mix of content presentation and activity/problem practice. There will be some required pre-work.
• Sections on Thursday in various times. Led by TAs; held live in person and not recorded. Additional review, discussion, and practice; mostly practice problem. Double-check your MyUW again before section because rooms may change. Materials will be released after section.
• No attendance is taken; there is no need ot notify absences.

Pedagogy

• You didn’t learn how to ride a bike by being taught how to ride a bike.
• Learn by doing; do not expect to sit down and write code the first time successfully. Practice and expect failure.

Learning in CSE 142

1. Exposure - lessons, video, textbook. Encounter concepts for the first time.
2. Guided practice - lesson activities, sections, labs. Practice with support from course staff.
3. Independent/Group Practice - checkpoints, section problems, additional practice.
4. Assessment - take-home assessments. Build upon steps 1-3 scaffolding, learn by doing and demonstrate mastery.
   • Expect to practice, make mistakes, and do things more than once.
   • Question-oriented.

Week 1 Friday Lecture

Java

• Programs begin with public class.
• All lower-case letters in keywords.
• Only allowed to use letters, numbers, underscores, and dollar signs.
• Conventions for this class - use pascal casing (e.g. HelloWorld, ByeNow).
• Program names must be descriptive.
• Use tabbing and indentation.
• public stratic void main(String[] args) - entry point, will use in the beginning of most every Java program.
• Command, method call - tells the program to do something.
• String - text, indicated by double quotes.
• Most lines in Java (statements) end w/ a semicolon.
• Methods - take a chunk of code and give it a name. Adds structure to the code and allows for repeated code to be called easily.
• Method names begin with a lower letter, whereas program names begin with an upper letter.

Assessment and Grading

• The goal of the course is to master the concepts and skills being taught.
• Work assessments are a proxy for mastery, and the final grade should reflect the extent to which you have demonstrated course objective mastery.
• Take-home assessments (weekly, 8), checkpoints (checkpoints, 9-10), culminating assessments (2), reflections (8-10)

Week 2 Monday Lecture

Administrative

• Large programming assignments to assess mastery of the week’s concepts. Make up the bulk of assignments.
• Credit for a checkpoint is to get the small-check mark.
• Culminating assessments (series of problems overing all material up to that point)
• Reflections with other assignmentsaa - put some time and thought into it
• ESNU grading: final grades will be assigned based on the amoutn of work at each level.
  • Visit the syllabus for ESN table.
  • Count how many reflections, checkpoints, etc. - compute the bundle and find the highest of guaranteed grades that you completely qualify for.
  • After the bundles, there will be bumps; credit will be given and adding it to the base grade.
  • The bumps are not given by a preset grading distribution. Accounts for changes in the course.
• Resubmission: one previous take-home assessment can be resubmitted each week.
• Collaboration policy: you can discuss ideas and approachess at a high level.

Java

• Use System.out.println() instead of System.out.println("").
• Use methods to capture structure; don’t put all code in the main function.
• There is not one right way to write code.
• Be able to defend your choice.
• Redundancy: we don’t want to repeat code unnecessarily. The more you type, the more likely you will make an error.
  • Current definition: 2 or more lines of code that are exactly the same in 2 or more places in your program.
  • A single line of code cannot be redundant.
  • We make a few exceptions to the redundancy rule, including blank lines.
• Methods can call other methods.

Week 2 Wednesday Lecture

• Control Flow Construct: the order in which operations are executed.
• So far, we have used linear control flow.
• Loop - a mechanism to make a chunk of code execute an integer number of times.
• Syntax: for (int i=0; i<n; i++) {...}.
  • Initialization, condition, update method
• Assignment - setting a variable to a value.

Week 2 Friday Lecture

• Counting loop; waiting until a condition happens.
• Initialize vcounting variable once; test the condition; repeat until condition is violated.

Week 3 Monday Lecture

Administrative

• Look at feedback and make sure you are taking advantage of given information.
• Highly important and recommended to reference resources.

Java

• Class constants - public static final int VAR = VAL;.
• Truncated/floor division.
• Modulus - remainder.

Week 3 Wednesday Lecture

Administrative

• Resubmission Cycle - fill out a Google form and provide the Ed URL in addition to remarking your submission.

Java

• Scope - where are things visibe to each other?
• A variable declared in one method is not visible in another method.
• Parameters -what we do when we call the method and what we do in the method that accepts the parameters.
• Never use global variables.
• import java.util.* - import directive. Put at top of script. We must ask to get access to this.
• Scanner is a class in Java - performs input.
• Scanner console = new Scanner(System.in); int input = console.nextInt(); - connects to the computer input.

Week 3 Friday Lecture

• Procedural programming - verb, noun structure.
• Java is designed for object-oriented programming rather than procedural programming.
• A class defines the structure of an object; an object is the thing itself.
• Scanners - Scanner console = new Scanner(System.in); int input = console.nextInt(); String strInput = console.next().
• Pass the console as a parameter to a method using user input.

Week 4 Monday Lecture

Administrative

• Things are ramping up and we are getting into the meat of the coruse.
• Moving from feeling uncomfortable to unsure.

Java

-char vs String

• Return values; we must recognize how to use the return value.
• If you want a method to return something, replace void with the output type.

Week 4 Wednesday Lecture

• Return values - a method to pass information throughout different methods.
• Store returned values in a variable, do not assume that variables themselves have been passed.
• If you want to concatenate characters into a string, use ""+char1+char2+char3.
• Conditionals/branches/if statements.

if (condition) {
  doSomething();
}

• num == 0
• if/else if/else

Week 4 Friday Lecture

• Pseudocode - planning programs without worrying about syntax.
• Cumulative programs.

Week 5 Monday Lecture

• A method should complete one task - don’t chain methods.
• Main should drive the program. Methods should complete their own work rather than dictating what should come next.
• Reading in multiple words: console.nextLine(); don’t mix nextLine with anything else.
• We cannot use == with Strings in the way we want it to. Strings are objects (i.e. not primitives); this tests if the two objects you are comparing are exactly the same object - not if it holds the same information.
  • Use String.equals(String) instead.
• Use while loop

Week 5 Wednesday Lecture

Administrative

• Simulated Midterm - write what a midterm would have looked like.
• A key for the simulated midterm will be released; you will be asked to annotate the midterm and make notes on what you didn’t do correctly.

Java

• Fencepost problems: posts and wire.
• Also can be known as a sentinel loop.

Notes discontinued after Week 5.