CPSC150

1. CPSC150 Week 6 notes Chapter 5 and other topics

2. toString • Try to print any class • Many print “garbage” (e.g., an address) • All classes inherit from Object which has a toString method that prints the address • You can override Object’s toString method • Modify Quiz 2 to use toString method • Write a toString method for every class you write

3. public class Student { private String name; private double gpa; // constructor and accessor and mutator methods public String toString( ) { return (“Student : “ + name + “ with “ + gpa + “GPA” + “\n”); } public void printStudent( ) { System.out.println(this); } Now, rewrite Course method

4. JavaDoc Documentation • View in BlueJ through Interface • View on web through API documentation (application programming interface): • http://java.sun.com/j2se/1.5.0/docs/api/ • Write your own /** Here is what my Class does * can go over multiple lines */

5. JavaDoc: write your own • Write in html (text IS html) /** Here is my <b>important</b> part */ • Use tags: @author your name @version date or 1.0 @param name description @return description • For a full list of tags, see: http://java.sun.com/j2se/1.5.0/docs/tooldocs/solaris/javadoc.html

6. Using the API • Use API whenever you want to do something, but don’t know how Example: How do I use Random numbers? • Look at API for Random • Or, Look at documentation for classes: • http://java.sun.com/j2se/1.5.0/search.html • (note: search isn’t always that helpful) • Or, look at: http://java.sun.com/j2se/1.5.0/docs/ • This has a more graphical representation than the API; most people use the API • Look at top description and each method summary

7. Random java.util.Random javadoc http://java.sun.com/j2se/1.5.0/docs/api/java/util/Random.html

8. import java.util.Random; import java.util.ArrayList; public class MyNumbers { // use Integer wrapper because ArrayLists must have object types ArrayList<Integer> nbrs = new ArrayList<Integer> (); Random random = new Random(); public MyNumbers() { // don’t need to do anything } public void addNumber( ) { nbrs.add(random.nextInt()); // nextInt from javadoc } public String toString( ) { String toReturn = ““List of Numbers is: ”; for (int i : nbrs) toReturn = toReturn + i + “ “; return toReturn; }

9. Math Library • in java.lang.Math • java.sun.com/j2se/1.5.0/docs/api/java/lang/Math.html • Lots of methods, all static. public class MathDemo { public MathDemo() { // don’t need anything} public double findDoubleMin(double a, double b) { return Math.min(a, b); } // no object needed }

11. ArrayList Exercises • Assume that a Book class exists that has a title (type String), author (type String) and call number (type int). Assume that Book has a toString method and accessor and mutator methods for all three fields. • Write a Library class that has an ArrayList bookList. Use generics. Create the following methods: addBook, printBook, and removeBook. Use a foreach loop for printBook. Just worry about title and author for now. • Write a method addBookBunch which accepts an array of Books and adds each to the bookList.

12. More on Library • Add a method addCallNbrs which assigns a call number to each book in the library. The call numbers should be sequential starting at 10 and adding 10 for each book (so the first 5 call numbers would be 10, 20, 30, 40, 50). • Revise the earlier methods to include adding call numbers. The call number should be reported to the user in printBook, but addBook should generate a call number, not request one from the user.

13. More ArrayList exercises • Rewrite your Course class from Quiz 2 so that, instead of using two Student objects, you use an ArrayList to hold all Students. • Create a class FillCanvas that creates Circles at random places (between 0 and 300 for both x and y) and of random size (between 0 and 300). Have a private getNewCircle method that creates one new Circle (but does not draw it). Write a public Fill10Circles method that puts 10 random circles in a circles ArrayList (by calling getNewCircle 10 times). • Write a method drawCircles that draws all of the circles in the ArrayList circles. • Write a method drawCirclesOneAtATime that draws the circle, then erases it, then draws the next circle.