CS 1 Java Programs Colorado State University Department of Computer Science Announcements Learning Objectives To understand the components of a Java program Due Date Reminders zyBooks Chapter 1 Today ID: 774036
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CS 1: Java Programs Colorado State University Department of Computer Science
Announcements Learning Objectives To understand the components of a Java program Due Date Reminders zyBooks Chapter 1 – Today Program 1 - Monday
Think-Pair-Share: Application Essentials On a piece of paper, write: 2-4 components you think are essential to a computer application Pair with a partner Discuss the ideas you wrote down Share the answers with others Share the answer with another group next to you (or same table)
Imports: lets your program use other code. For example: import java.util.Scanner;Class name: the name of the organizational unit in Java. Must start with uppercase letter. Entry point: where the program starts. In Java: main() Statements: the base unit of code. Represents a single, simple action. Ends with a semicolon. ';'Reserved words: have special meaning and can’t be used for anything else. "class", "public"... Blocks: organize your program and help the computer read it. Defined by braces: { }Comments: help people reading the code! Can be line: // a single-line comment, or block: /* can span many lines! */ Anatomy of a Java Program
Whitespace means any part of some text that isn’t a symbol. Think spaces, tabs, etc.In Java, whitespace doesn’t change the way the program works.It’s a good idea to use good indentation and spacing to make your code easier to understand . public class Avatar { public static void main(String[] args) { String favoriteElement = "water"; System.out.println("My cabbages!"); } } Whitespace in code Indentation Spacing Pro Tip: Auto-Indent Many IDE’s support auto-indentation! In Eclipse, it’s Ctrl + I
In programming, there are many conventions around style choices.Brace positioning, variable names, etc…It’s usually good to choose a convention. Be consistent ! Don’t mix and match. public static int answerToTheUniverse() { // brace-up style int variable_with_underscores = 42; } String getSomeText() { // brace-down styleString camelCaseVariable = "<3"; } Convention
Let’s practice! Write declarations for variables to store some pieces of information. Pick a style and be consistent.Example: A student’s name => String studentName; Try these: The radius of the Earth in miles The character at the end of a sentence Your favorite ice cream flavor Then, think about the two brace placement styles (brace-up and brace-down). Which do you prefer? Why? Compare your variables and brace reasoning with a friend. Try it yourself
Compile Error: a problem with the actual text of the codeDetected by the compiler. Code will not runExamples: mismatched braces, missing semicolons Runtime Error: the code runs, but crashes/aborts Encountered at runtime Examples: divide by zero, index out of boundsLogic Error: the code will run and doesn’t crash, but gets the wrong answer Could be caused by a typo, or a misunderstanding of the logic Examples: adding instead of subtracting, off-by-one Types of programming errors
Think-Pair-Share: Organizing functionality On a piece of paper, try to come up with examples of: A syntax error A runtime error A logic error Pair with a partner Talk about the error examples you came up with Share the answers with others Share the answer with another group next to you (or same table)