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Building a Simple Java Database Program for Car Entries with Search Capabilities

This project outlines the development of a basic Java database program specifically designed for managing car entries. It introduces features such as parallel arrays for different attributes (make, style, color, owner, year) and allows users to perform searches using various criteria. The program includes functions for displaying all entries and implementing a simple search mechanism by matching specified parameters. It highlights the importance of query-based operations in database management, aiming for simplicity and usability in data retrieval.

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Building a Simple Java Database Program for Car Entries with Search Capabilities

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  1. Today’s topics Java The Database Program Upcoming Recursion Reading Great Ideas, Chapter 4

  2. Database • Extend ideas used in phone program • Can have many “parallel” arrays • Design Used Car Database Make Style Color Owner Year

  3. Basic Functions • What do we expect of a database program? • Load Data (file I/O would be nice) • Display Data (complete dump) • Edit/Update (make corrections, add more data) • Query/Search (selective info retrieval) • What are we actually going to implement? • Know no file I/O: build data in • Will have a way to display all • This program will not attempt edit/update • Queries are the key to making this useful

  4. Naïve Query • Use same approach as telephone lookup • Specify value for only one of the lists • E.g. , specify Ford • Get all entries that are Fords • OK for small lists like this toy example • What is the problem here? • ? • Similar problem for using any other singlespecification

  5. More Queries • Other Simple Query • The example has 5 lists • Specify what we want to match in each list • E.g. Ford, truck, blue, M.Ramm, 1972 • Very limiting • Can really only expect a True/False response of this • We either get a “hit” or we do not • Wild Card Specification • Can specify that we do not care about one or more lists • Adds surprising versatility! • E.g. Mercedes,4 door,don’t-care,don’t-care,don’t-care • Yields multiple responses for this example

  6. Database Program public class UsedCars extends java.applet.Applet implements ActionListener { TextField gMake, gStyle, gColor, gOwner, mInstruct; IntField gYear; String Make[] = {"Mercedes","Mercedes","Ford","Mercedes","Datsun","Ford“ }; String Style[]= {"4 door", "4 door", "truck", "4 door", "2 door","4 door"}; String Color[]= {"white", "ivory", "blue", "green", "red", "blue“ }; String Owner[]= {"M.Ramm", "D.Ramm", "M.Ramm","D.Ramm", "K.Ramm","D.Ramm"}; int Year[] = { 1987, 1987, 1972, 1971, 1978, 1978 }; Label make, style, color, owner, year; Button bSearch; TextArea mResults; int size = 6;

  7. Database Program.2 public void init() { year = new Label("Year"); make = new Label("Make"); style = new Label("Style"); color = new Label("Color"); owner = new Label("Owner"); mInstruct = new TextField(60); mInstruct.setText( "Enter Selections, leave blank for Wild Card"); gYear = new IntField(10); gMake = new TextField(10); gStyle = new TextField(10); gColor = new TextField(10); gOwner = new TextField(20); bSearch = new Button("Search"); mResults = new TextArea(10, 60);

  8. Database Program.3 bSearch.addActionListener(this); add(mInstruct); add(year); add(gYear); add(make); add(gMake); add(style); add(gStyle); add(color); add(gColor); add(owner); add(gOwner); add(bSearch); add(mResults); } public void actionPerformed(ActionEvent event) { int yea; String mak, sty, col, own; yea = gYear.getInt(); mak = gMake.getText(); sty = gStyle.getText(); col = gColor.getText(); own = gOwner.getText(); mResults.setText("Cars Matching Parameters Specified\n"); report(yea, mak, sty, col, own, size); }

  9. Database Program.4 boolean isMatch(int year, int yea, String make, String mak, String style, String sty, String color, String col, String owner, String own) { if ((year == yea || yea == 0) && (make.equals(mak) || mak.equals("")) && (style.equals(sty)|| sty.equals("")) && (color.equals(col)|| col.equals("")) && (owner.equals(own)||own.equals("")) ) { returntrue; } returnfalse; }

  10. Database Program.5 void report(int yea, String mak, String sty, String col, String own, int num) { int k = 0; while (k < num) { if (isMatch(Year[k], yea, Make[k], mak, Style[k], sty, Color[k], col, Owner[k], own)){ mResults.append("year:" + Year[k] + "make:" + Make[k] + " style:" + Style[k] + "color:" + Color[k] + " owner:" + Owner[k] + "\n"); } k = k + 1; } } }

  11. Other possible Features • Allow output of counts rather than displaying field • Permit logical expression, not just matching • E.g., Ford | Chevy • For numeric data allow ranges • E.g., 1999 < year < 2003 • Allow merging or joining of databases • This capability is called a Relational Database • Like having multiple database all linked together

  12. Relational Databases • Possible Duke Databases: Students Name, Year, Major, Schedule, … Classes Dept, Number, Section, Instructor, Times, Location, Roll, … Rooms Building, Number, Capacity, AV, … Courses Dept, Number, Title, Type, Description, Prerequisites, … • Possible Queries (Reports): • Class Roll: Which of the databases above are needed?

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