Introduction to Programming - m r s g l a z e r o n l i n e

1、Introduction to JavaThe Programming ProcessThe programming process1. Understand the problem2. Design a solution3. Run and debug.AlgorithmsWhat is an algorithm? An algorithm is an ordered plan not in a specific computer language. Is order important? You bet it is. Look at the following set of actions

2、. Wet hairRinseAdd shampooRepeatLatherWhat is being described?You are correct. Its the act of shampooing hair. Note the order; it is incorrect. If the operation was completed following these instructions as printed above, the person would be bubbly and not clean. ORDER IS IMPORTANT!Think about build

3、ing a peanut butter and jelly sandwich. Put peanut butter on one side of bread. Put jelly on another side of bread.What if we put the peanut butter on one side of a slice of bread and the jelly on the other side of the same slice? It would be messy and not very easy to eat! BE VERY SPECIFIC!The JAVA

4、 Development ProcessSource CodeWhat is source code? Its the code you type in the editor, your program.CompilerWhat is the compiler? The compiler translates the program (the users instructions) into machine language in ahead of the program run. During this action, the compiler will check for spelling

5、 and other syntax errors. Each machine has its own specific machine code.Interpreters An interpreter, like a compiler, translates the program code into machine language; however, unlike the compiler the program translates each line of code as it is executed.The Java Virtual MachineThe system where a

6、 program is translated into a general machine language called bytecode by a device called a compiler-interpreter. This general (generic) machine language allows for the portability of the program. Java bytecodes are machine-independent; it is semi-compiled code that allows your Java code to be trans

7、mitted over the Internet and executed on another computer even if that computer is of an entirely different type.Execution Here is where the logic/programming errors occur. (The program runs but the results are not correct).Editors, Compilers, and the Software Design ProcessIf there are errors, revi

8、se The EDITOR(where you type the program)Checks for Syntax ErrorsThe CompilerOKAYBytecodePCVirtual MachineMac, etcVirtual MachineHow does Java work? Other High Level LanguagesIf there are errors, revise The EDITOR(where you type the program)Checks for Syntax ErrorsThe Compiler: checks for errorsOKAY

9、BytecodePCVirtual MachineMac, etcVirtual MachineTranslator: translates source code into bytecodeJavaIf there are errors, revise The EDITOR(where you type the program)Checks for Syntax ErrorsThe CompilerOKAYByte codePCVirtual MachineMac, etcVirtual MachineNote: The translator is “missing. The Java Vi

10、rtual Machine (JVM) compiles and translates into byte code in one operation. This is done via software and not hardware. One should also be aware that the byte code generated by the JVM will run on any machine (MAC, PC, UNIX). The source code is the same for Macs, PCs, etc.What is Java?Java is a pro

11、gramming language written in byte code. A source program is a text file that contains a program (such as above) written in a programming language ://java5. An applet sends byte code from one computer to another via the Internet. The Programming ProcessThe programming process4. Unders

12、tand the problem5. Design a solution6. Run and debug.Programming in JavaA Java program is composed of classes (as few as one, as many as ). We begin with output to the monitor. The complete program below will output to the monitor the phrase: HELLO WORLD! / Print demo / program description (not code

13、)/ Ella Glazer 8 03/ your name and date public class Hello/ class declarationpublic static void main(String args ) / this is the main method System.out.println("HELLO WORLD!"); /statements (lines of code) / end main ./ end class1. Note that public, class, etc. is in lower case. Java is cas

14、e-sensitive. 2. The brackets ( ) denote the beginning and ending of a class, method, etc.3. Every Java program (not applets) has a main method. 4. Static variables and methods: when information must be shared among all instances of a class. More on Static later.5. Every Java program main method has

15、a return type. In this case, void means nothing is returned.6. The name of the method (in this example and for most of this course) is main.7. WHITE SPACE: In order to keep the programs readable we will be using a lot of white space which consists of indenting and skipping lines. Remember I am readi

16、ng and grading these programs. Note the indenting. While not required it makes reading the code easier.8. Comments: There are lines in a program that are not part of the program but are important, such as your name, description of what the program does, or assignment #, etc. / or /* */. This is call

17、ed documentation.9. Class Naming Conventions: classes are usually named with an upper case letter. Whats the name of the class used above?10. public static void main ( String args ) shows where the program will start running. The word main means that this is the main method - where the Java virtual

18、machine (The abstract computer on which all java programs are run.) will start running the byte code version of the program. 10. ; Every statement ends with a semicolon.11. System.out.println(" Hello World "); This statement writes the character(s) inside the quotation marks to the monitor

19、 of the computer system and takes the cursor to the next line while System.out.print (“something); will leave the cursor at the last item printed.How to hand in assignments. · Run it, · Copy the output and put into a Word document· Copy the code and put it into the same Word document as above.· Attach to an email to put your name and class in the subject./*print demo by E.Glazer 8-13*/Note: anything inside /* */ is a comment public class