Introduction to Java Programming. Instructor: Renzhi Cao Computer Science Department Pacific Lutheran University Spring 2020

Transcription

1 Introduction to Java Programming Instructor: Renzhi Cao Computer Science Department Pacific Lutheran University Spring 2020

2 Files and the CSCI Systems Map: access as if it were a local disk. Lab Computer The X: drive CSCI Server (river.cs.plu.edu) Home Computer SFTP or SSH Copy Must make a copy, make changes, then copy back. CSCI Server (haven.cs.plu.edu) See: for help. PLU Computer Science 2

3 What is Java? What does a Java program look like? How do I go about writing a Java program?

4 What is Java?

5 Java is an object-oriented programming language developed at Sun Microsystems in Examples of structural and object-oriented programming

6 Algorithm Program

7 Automobile C02 Calculator Ask the user for miles per gallon Ask the user for the number of miles driven Calculate the gallons of fuel used Calculate pounds of CO2 used (gallons of fuel used times the emissions factor of 19.6) Display gallons of fuel and CO2 used algorithm

8 CPU: Central Processing Unit The brain of the computer. Types: Intel: Core i5, Core i7, Pentium, Core Duo, AMD: Bulldozer, Athlon, Opteron, Motorola: 68000, PowerPC, ARM: ARM11, Cortex, ARM3, CPUs (Processors) may speak different languages.

9 The CPU Understands only one language

10 What does a Java program look like?

11 // calculates pounds of C02 emitted by a gasoline powered automobile public class CO2Calculator { public static void main(string[] args) { int milesdriven = 360; double mpg = 24.5; double gallonsused, co2used; double emissionsfactor = 19.6; // calculate gallons of fuel used gallonsused = milesdriven/mpg; } } // calculate and display pounds of C02 emitted co2used = gallonsused * emissionsfactor; System.out.println("You used " + co2used + " pounds of C02 );

12 program structure ClassA statement1 statement2 statement3 methodone methodtwo ClassB

13 Java code // comments about the class public class C02Calculator { class header class body }

14 Java code // comments about the class public class C02Calculator { // comments about the method public static void main (String[] args) { } method body method header }

15 Reserved words public class C02Calculator { public static void main (String[] args) { } }

16 Java reserved words abstract boolean break byte case catch char class const continue default do double else extends false final finally float for goto if implements import instanceof int interface long native new null package private protected public return short static strictfp super switch synchronized this throw throws transient true try void volatile while

17 Identifiers public class C02Calculator { public static void main (String[] args) { } }

18 Rules for Identifiers An identifier can be made up of letters, digits, the underscore character ( _ ), and the dollar sign ( $ ) Identifiers cannot begin with a digit Java is case sensitive - Total, total, and TOTAL are different identifiers By convention, Java programmers use different case styles for different types of identifiers, such as title case for class names - Lincoln upper case for constants - MAXIMUM

19 class CLASS 1time abc123 bank-account bank_account $hello _1CS144 _class -time123 Identifying identifiers: is it valid or not?

20 Variables 0x000 0x001 0x002 0x003 0x004 0x005 0x006 0x007 memory 360 Java code int milesdriven = 360; variable milesdriven is a symbolic name for the memory location 0x003.

21 How do I go about writing a program?

22 edit compile execute

23 Program Development Process Text editor Saves Java statements Source code (.java)

24 Text Editor: Atom

25

26 Program Development Process Text editor Java compiler Is read by Produces Source code (.java) Byte code (.class)

27 Java Compiler: javac

28 Program Development Process Text editor Source code (.java) Java compiler Java Virtual Machine Is interpreted by Results in Byte code (.class) Program Execution

29 Java Interpreter: java

30 compilation/syntax errors

31 logic errors

32 Let s give it a try