201707 CSE110 Lecture 03
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This document covers a lecture on classes, methods, and variables in Java programming. It discusses the main() method as required for all Java programs, the use of static keywords, and provides examples of classes with and without a main() method. It also covers identifiers, comments, variables, and primitive data types in Java. The homework assigned is to read sections 2.1, 2.2, and 2.3 of the textbook.
![Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 17
Comments
public class MyProgram {
}
public static void main (String[] args) {
}
/**
* comments about the class
*
*/
// comments about the method
method
body](https://image.slidesharecdn.com/cse110l03-types-170708035920/85/201707-CSE110-Lecture-03-17-320.jpg)
201707 CSE110 Lecture 03
- 1. CSE110 Principles of Programming with Java Lecture 03: Classes, methods, and variables Javier Gonzalez-Sanchez javiergs@asu.edu javiergs.engineering.asu.edu Office Hours: By appointment
- 2. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 2 Previously… public class TheClassName { } public void theFirstMethodName() { } public void secondMethodName() { } // instructions go here // instructions go here // variables go here // variables go here // variables go here
- 3. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 3 Previously…
- 4. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 4 main() method • All programs should have one and only one main() method. • Trying to execute a class without a main() method generates a compilation error
- 5. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 5 static public class TheClassName { } public static void theFirstMethodName() { } public static void secondMethodName() { } // instructions go here // instructions go here // variables go here // variables go here // variables go here
- 6. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 6 Example without main()
- 7. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 7 Example with main()
- 8. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 8 Example main() calling methods
- 9. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 9 static public class TheClassName { } public static void theFirstMethodName() { } public static void secondMethodName() { } // instructions go here // instructions go here // variables go here (static also) // variables go here // variables go here
- 10. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 10 Error
- 11. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 11 Fix the Error
- 12. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 12 12 Previously… • The 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
- 13. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 13 Identifiers • Identifiers are the words a programmer uses in a program • 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 o title case for class names - Lincoln o upper case for constants - MAXIMUM 13
- 14. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 14 White Space • Spaces, blank lines, and tabs are called white space • White space is used to separate words and symbols in a program • Extra white space is ignored • A valid Java program can be formatted in many ways • Programs should be formatted to enhance readability, using consistent indentation
- 15. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 15 15 Comments • Comments in a program are called inline documentation • They should be included to explain the purpose of the program and describe processing steps • They do not affect how a program works • Java comments can take three forms: // this comment runs to the end of the line /* this comment runs to the terminating symbol, even across line breaks */ /** this is a javadoc comment */
- 16. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 16 16 Comments public class MyProgram { /* */ } // comments about the class class bodyComments can be placed almost anywhere
- 17. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 17 Comments public class MyProgram { } public static void main (String[] args) { } /** * comments about the class * */ // comments about the method method body
- 18. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 18 Variables • Multiple variables can be created in one declaration int count, temp, result; • A variable can be given an initial value in the declaration int sum = 0; int base = 32, max = 149; • An assignment statement changes the value of a variable total = 55;
- 19. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 19 Data Types § There are exactly eight primitive data types in Java § Four of them represent integers: byte, short, int, long § Two of them represent floating point numbers: float, double § One of them represents characters: char § And one of them represents boolean values: boolean
- 20. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 20 Homework Read Sections 2.1, 2.2, and 2.3
- 21. CSE110 - Principles of Programming Javier Gonzalez-Sanchez javiergs@asu.edu Summer 2017 Disclaimer. These slides can only be used as study material for the class CSE110 at ASU. They cannot be distributed or used for another purpose.