Java Java programming concepts Downloading the JDK Java

Java Concepts ▮ Java source code stored in files with an extension of. java

Java Concepts Cust. java (Java file) Cust. class (Class file) Java source code Editor

Java Concepts ▮ Review: files with an extension of. java contain source code ▮

Java Virtual Machine (JVM) ▮ JVM is “the place” (i. e. s/w) where the.

Java Virtual Machine (JVM) ▮ To run a java application on a computer you

JDK (aka JSDK) Chapter 1 © copyright Janson Industries 2015 7

JDK on the PC ▮ Java JDK 8 is an example ▮ Use IE

JDK on the PC ▮ To install the JDK: ▮ Run jdk-8(u#)-windows-i 586 -p.

Select the latest JDK version Chapter 1 © copyright Janson Industries 2015 10

Scroll down and click the accept agreement radio button Double click the 32 bit

Specify to save the file by clicking the Save drop down button and then

Create and save to a folder called jdkzip on your thumb drive (or the

Using File Explorer open the jdkzip folder Chapter 1 © copyright Janson Industries 2015

JDK on the PC ▮ Only takes up 180 meg ▮ Final install will

If you get this, you downloaded the wrong JDK Chapter 1 © copyright Janson

Or this (or any other msg), you downloaded the wrong JDK Chapter 1 ©

Accept the default components (notice the JRE is just one part of the JDK)

To save on typing later, we’ll change directory to just JDK i. e. F:

JDK install window redisplayed with new location Click Next Chapter 1 © copyright Janson

Shows where JRE will be installed. Change to… Some students tell me this screen

Choose drive to save to, then click Make New Folder Then specify jre, click

JRE install window redisplayed with new location Chapter 1 © copyright Janson Industries 2015

You may have to shut down some running apps Chapter 1 © copyright Janson

And again… Chapter 1 © copyright Janson Industries 2015 25

Two folders called jdk and jre are created (verify with File Explorer) Delete jdkzipjdk-8(u#)-windows-i

To verify that you installed correctly, display the contents of jdk/bin folder and make

JDK Install Problems? ▮ Error 1723 occurred in the installer package ▮ Lot’s of

Running a pgm ▮ When you run an application in Windows, you are specifying

Running a pgm ▮ For instance, clicking the IE icon tells Windows to “run”

▮ C: Program FilesInternet Exploreriexplore. exe is a fully qualified file name Chapter 1

Running a pgm ▮ If a fully qualified file name is not specified, Windows

Running a pgm ▮ Let’s prove it ▮ In command prompt we specify iexplore.

Running a pgm ▮ Now we will set the path value ▮ path =

Running a pgm ▮ JDK must be in the PC’s path to access the

Will use Notepad++ to enter source code and save to a file Download Notepad++

Save As to your thumbdrive (so you can run anywhere) Chapter 1 © copyright

Click Run, then OK Chapter 1 © copyright Janson Industries 2015 38

Click Next then I Agree Chapter 1 © copyright Janson Industries 2015 39

Specify a location on your thumbdrive (so you can run from anywhere) then click

If installing to thumbdrive select first option, if not select third option Click Install

Close change. log Chapter 1 © copyright Janson Industries 2015 42

Enter source code as follows (ignore colors) Then click File, Save Running a pgm

Java Rules ▮ File name (Customer) has to match class name (Customer) ▮ Executable

Running a pgm Start Notepad++, enter source code, and save file with type of

Running a pgm A couple java rules: File name (Customer) must match certain statements

Running a pgm Bring up the Command Prompt by clicking: Start, All Apps, Windows

Running ▮ When javac and java commands are run, at first they do the

Running ▮ The current/default directory is displayed in the command prompt ▮ In this

Running ▮ 1. Issue the path command so that jdk/bin is in the path

Running Customer. java is on F: current directory is H: so “file

Possible Problems? ▮ javac or java command is not recognized ▮ Why? Path not

Possible Problems? ▮ When there are syntax errors, JVM will show: ▮ A message

Possible Problems? ▮ Java syntax errors ▮ Upper case/lower case letters are different ▮

In Class Exercise ▮ Create Customer. java and enter the source code using notepad

Non-graded Assg 2 ▮ Create a java file called Yay that displays the following:

Non–graded Assg 2 ▮ When Yay is run the output should look like this:

Graded Assignments ▮ You will have to download lab files (Word documents) for the

Java ▮ Java Language Companion (JLC) guide ▮ This is the Java text book

http: //web. fscj. edu/Janson/COP 1000/ Chapter 1 © copyright Janson Industries 2015 60

No graded assg until C 2 but you can start before Chapter 1 ©

The Word doc contains several non-graded assgs (labs) and one graded assg (usually the

Slides: 62

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Java ▮ Java programming concepts ▮ Downloading the JDK ▮ Java coding and executing example Ch 1 Assg 2 This presentation can be viewed on line at: Chapter 1 © copyright Janson Industries 2015 1 http: //web. fscj. edu/Janson/COP 1000/ch 01 a. Introto. Java. ppt

Java Concepts ▮ Java source code stored in files with an extension of. java ▮ The source code is “compiled”, meaning: ▮ Translated into bytecode ▮ Bytecode stored in class files (files with an extension of. class) ▮ Bytecode is a “cross-platform program representation” that is non-executable Chapter 1 © copyright Janson Industries 2015 2

Java Concepts Cust. java (Java file) Cust. class (Class file) Java source code Editor (Notepad++) Java source code Programmer Chapter 1 CPU Java bytecode Compiler javac Cust. java Programmer © copyright Janson Industries 2015 JVM main method in Machine Language java Cust Programmer 3

Java Concepts ▮ Review: files with an extension of. java contain source code ▮ Review: files with an extension of. class contain “bytecode” ▮. java files are “compiled” (javac command) to create. class files ▮ Bytecode is a cross-platform program representation that is non-executable ▮ New: bytecode needs to be translated to machine language (java command) Chapter 1 © copyright Janson Industries 2015 4

Java Virtual Machine (JVM) ▮ JVM is “the place” (i. e. s/w) where the. class files (i. e. programs) are translated ▮ The JVM is invoked with the java command ▮ The JVM translates bytecode into machine language and sends to CPU for execution (i. e. program is run) ▮ Therefore, each "type" of computer needs a unique JVM Chapter 1 © copyright Janson Industries 2015 5

Java Virtual Machine (JVM) ▮ To run a java application on a computer you must download a JVM/JRE (java runtime environment) ▮ But to compile you also need the java compiler ▮ Oracle (and many other vendors) offer ▮ Oracle has a JDK (Java Development Kit) that includes a JRE and the compiler Chapter 1 © copyright Janson Industries 2015 6

JDK (aka JSDK) Chapter 1 © copyright Janson Industries 2015 7

JDK on the PC ▮ Java JDK 8 is an example ▮ Use IE (not Chrome) to download the JDK: ▮ http: //www. oracle. com/technetwork/javase /downloads/index. html ▮ Select the latest version ▮ Click on the JDK download button for the latest update (i. e. JDK 8, or JDK 8 u 60, etc. ) ▮ Select the JDK for your computer (i. e. Windows) ▮ Download to thumb drive (G: ) or your C drive Chapter 1 (at home) © copyright Janson Industries 2015 8

JDK on the PC ▮ To install the JDK: ▮ Run jdk-8(u#)-windows-i 586 -p. exe (where # is the latest version and update numbers) ▮ During the install, create folders to hold the JDK and JRE called jdk and jre ▮ Delete the original. exe file jdk-8(u#)-windows- i 586 -p. exe Chapter 1 © copyright Janson Industries 2015 9

Select the latest JDK version Chapter 1 © copyright Janson Industries 2015 10

Scroll down and click the accept agreement radio button Double click the 32 bit operating system version (Windows x 86) Chapter 1 © copyright Janson Industries 2015 11

Specify to save the file by clicking the Save drop down button and then Save As Chapter 1 © copyright Janson Industries 2015 12

Create and save to a folder called jdkzip on your thumb drive (or the C: if you will always being work on that same computer) Chapter 1 © copyright Janson Industries 2015 13

Using File Explorer open the jdkzip folder Chapter 1 © copyright Janson Industries 2015 14

JDK on the PC ▮ Only takes up 180 meg ▮ Final install will take up ~ 180 meg ▮ Run the exe file by double clicking ▮ Click the Next button Chapter 1 © copyright Janson Industries 2015 15

If you get this, you downloaded the wrong JDK Chapter 1 © copyright Janson Industries 2015 16

Or this (or any other msg), you downloaded the wrong JDK Chapter 1 © copyright Janson Industries 2015 17

Accept the default components (notice the JRE is just one part of the JDK) Chapter 1 You can control where the JDK is installed © copyright Janson Industries 2015 by clicking the Change. . . button 18

To save on typing later, we’ll change directory to just JDK i. e. F: JDK (or C: JDK) then click the OK button Chapter 1 © copyright Janson Industries 2015 19

JDK install window redisplayed with new location Click Next Chapter 1 © copyright Janson Industries 2015 20

Shows where JRE will be installed. Change to… Some students tell me this screen doesn’t appear, if it doesn’t – no problem, skip the next two slides. Chapter 1 © copyright Janson Industries 2015 21

Choose drive to save to, then click Make New Folder Then specify jre, click OK 22

JRE install window redisplayed with new location Chapter 1 © copyright Janson Industries 2015 23

You may have to shut down some running apps Chapter 1 © copyright Janson Industries 2015 24

And again… Chapter 1 © copyright Janson Industries 2015 25

Two folders called jdk and jre are created (verify with File Explorer) Delete jdkzipjdk-8(u#)-windows-i 586 -p. exe and click the Close button Chapter 1 © copyright Janson Industries 2015 26

To verify that you installed correctly, display the contents of jdk/bin folder and make sure you have two executable files called javac and java Chapter 1 © copyright Janson Industries 2015 27

JDK Install Problems? ▮ Error 1723 occurred in the installer package ▮ Lot’s of possible reasons ▮ Click here for some suggestions Chapter 1 © copyright Janson Industries 2015 28

Running a pgm ▮ When you run an application in Windows, you are specifying an executable file name ▮ Executable files contain machine language ▮ On Windows machines these files have names that end in. exe Chapter 1 © copyright Janson Industries 2015 29

Running a pgm ▮ For instance, clicking the IE icon tells Windows to “run” iexplore. exe in C: Program FilesInternet Explorer Chapter 1 © copyright Janson Industries 2015 30

▮ C: Program FilesInternet Exploreriexplore. exe is a fully qualified file name Chapter 1 © copyright Janson Industries 2015 31

Running a pgm ▮ If a fully qualified file name is not specified, Windows searches ▮ 1. The default (aka current) directory ▮ 2. The locations stored in the Environment Variable called PATH ▮ I. e. path holds all the locations Windows should search when an unqualified file name is specified ▮ You can control the value of the Path variable ▮ Let’s prove it!! Chapter 1 © copyright Janson Industries 2015 32

Running a pgm ▮ Let’s prove it ▮ In command prompt we specify iexplore. exe ▮ “Not recognized” message ▮ Now specify fully qualified file name (in quotes) ▮ IE started Chapter 1 © copyright Janson Industries 2015 33

Running a pgm ▮ JDK must be in the PC’s path to access the compile (javac) and run (java) commands (as well as other stuff) ▮ Path holds locations of executable files ▮ Several ways to define path locations ▮ Each time you go to the command prompt (depending on where jdk installed) enter ▮ path=f: jdkbin or ▮ path=c: jdkbin Chapter 1 © copyright Janson Industries 2015 35

Java Rules ▮ File name (Customer) has to match class name (Customer) ▮ Executable statements ended with a semicolon (; ) ▮ System. out. println not System. out. print. In ▮ Stands for “print line” not “print In”. ▮ Open symbols - ( { [ - must have matching closing symbols - ) } ]. Chapter 1 © copyright Janson Industries 2015 44

Running a pgm Start Notepad++, enter source code, and save file with type of java F: Customer. java (must specify type as All Files) Save to the root of your thumbdrive (i. e. F: ) Change Save as type to Java source file then the file name to Customer. java (must leave. java in file name) Click Save Chapter 1 © copyright Janson Industries 2015 45

Running a pgm A couple java rules: File name (Customer) must match certain statements System. out. println() displays text Statements end in a semicolon (; ) Chapter 1 © copyright Janson Industries 2015 46

Running ▮ When javac and java commands are run, at first they do the same thing as Windows ▮ They check the default directory for the. java (source code) and. class (bytecode) files ▮ If files not there, "file not found" msg displayed ▮ Solution ▮ Change current directory to the location of the files with the CD (change directory) command ▮ CD F: , hit Enter, then type F: , hit Enter again Chapter 1 © copyright Janson Industries 2015 48

Running ▮ 1. Issue the path command so that jdk/bin is in the path ▮ 2. If necessary, change the default path to the location of the. java file to be compiled (i. e. F: ) (type CD F: , hit Enter, then type F: , hit Enter) ▮ 3. Convert to byte code (javac Customer. java) ▮ 4. Run the program (java Customer) Chapter 1 © copyright Janson Industries 2015 50

Running Customer. java is on F: current directory is H: so “file not found” Must change current directory to location of Customer. java (i. e. F: ) Customer. java found cause default directory is F: Chapter 1 © copyright Janson Industries 2015 51

Possible Problems? ▮ javac or java command is not recognized ▮ Why? Path not defined correctly. Common mistakes: wrong drive letter, incorrect directory name(s), extra spaces after bin, when installing you mixed up jdk and jre directories ▮ Customer not found: No. Class. Def. Found. Error, Class. Not. Found. Exception, could not find the main class ▮ Why? Chapter 1 Current directory not where Customer file is located or file name not specified correctly (extra spaces, etc. ) © copyright Janson Industries 2015 52

Possible Problems? ▮ When there are syntax errors, JVM will show: ▮ A message with useful info ▮ File name: Customer. java ▮ Line number that has the error: 10 ▮ What the problem is: ‘; ’ expected ▮ The source code statements that have errors with ^ under where it thinks there are problems Chapter 1 © copyright Janson Industries 2015 53

Possible Problems? ▮ Java syntax errors ▮ Upper case/lower case letters are different ▮ If example shows upper case letter, you must use upper case letter ▮ Forward slash/back slash are different ▮ println (means: print line) not print. In Chapter 1 © copyright Janson Industries 2015 54

In Class Exercise ▮ Create Customer. java and enter the source code using notepad ▮ Compile and run Customer 55

Non-graded Assg 2 ▮ Create a java file called Yay that displays the following: ▮ Yay! ▮ My first java program ▮ Send Yay. java as email attachment to me at rjanson@fscj. edu ▮ Specify the Email topic as Ch 01 Assg 2 56

Non–graded Assg 2 ▮ When Yay is run the output should look like this: 57

Graded Assignments ▮ You will have to download lab files (Word documents) for the graded assignments ▮ Create a folder on your memory stick to hold the files (and your work) called COP 1000 ▮ Download the labs from the folder Labs at the same location as the PP presentations 58

Java ▮ Java Language Companion (JLC) guide ▮ This is the Java text book ▮ In a PDF file at the same location as the PP presentations and labs ▮ Download and read 59