Thread: Exercise 115

I took care of exercise 105. I don't know what to do with 115 though. I've worked a little bit more and progressed a slight bit, but here's the exercise:

 
A team of biologists is conducting an experiment that involves collecting data on animals founds in a 1 km square area of woodland. As each animal is identified, a record is made of its name, the time of its discovery, and the initials of the scientist who found it. The data are to be recorded on a laptop. Design and implement a system for storing the data, and test your code thoroughly.
 
[Hint: Think in terms of creating an object for each discovery. What information should each object store, and in what will you store these objects?]

Here is my code:

// put class definitions here
 
 
 
public class Record{
 
    String name;
 
    String initials;
 
    String time;
 
 
 
    public Record{
 
        this.name = name;
 
        this.initials = initials;
 
        this.time = time;
 
    }
 
}

Here's another section for me to test my solution in:

public static void main( String[] args )
 
{
 
  // test your solution here
 
 
 
}

So I know I'm supposed to make a new Object out of the variables, but do I need to use getters and setters or something? If that was the case it would probably be a lot easier than I'm assuming.


Thx

Okay, well what you have right now is a default constructor. I would change that into a constructor with parameters.

public Record(name, initials, time)
{
 
}

Now you would be able to create an object with given values for those three instance fields!

Something you may not have learned yet is how to use multiple classes. A class can call another class if it is imported or if they are in the same package.

I would create a second class that is a "higher" level class. This class would store multiple instances of the class "Record".

In other words you would have an array that holds multiple "Record" objects.

Getters would be nice to view the individual instance fields or alternatively you could have a "displayRecord()" function in the Record class that displays all three instance variables.

Then in your larger function you could call the displayRecord() function for each object in your array of records!

So, how do I use multiple classes?

--- Update ---

I think that's just nesting classes right?

--- Update ---

For this example, what do I put in the subclass?

// put class definitions here
 
 
 
public class Record{
 
    private String name;
 
    private String initials;
 
    private String time;
 
 
 
    public Record(String name, String initials, String time){
 
        this.name = name;
 
        this.initials = initials;
 
        this.time = time;
 
    }
 
   public class diffRecords{
 
       diffRecords(){
 
       }
 
   }
 
}

First, build one class that includes all of the variables needed to completely describe and store a "discovery." To that class, add at least one constructor, perhaps more than one, and any getter and setter methods you think will be useful. Post that when you're done.

Here's my updated code:

// put class definitions here
 
 
 
public class Record {
 
 
 
   private String name;
 
 
 
   private String initials;
 
 
 
   private String time;
 
 
 
   public Record (String name, String initials, String time){
 
       this.name = name;
 
 
 
       this.initials = initials;
 
 
 
       this.time = time;
 
   }
 
 
 
   public String getName(){
 
       return name;
 
   }
 
 
 
   public String getInitials(){
 
       return initials;
 
   }
 
 
 
   public String getTime(){
 
       return time;
 
   }
 
 
 
ArrayList diffRecords = new ArrayList<Record>();
 
}

--- Update ---

I think there are syntax errors.

Your code is so simple yet hard to read because of the extra linefeeds, no comments, and inconsistent formatting. Please, start applying standard coding practices consistently. It would be much nicer if your code looked like:

public class Record
{
    private String name;
    private String initials;
    private String time;
 
    public Record ( String name, String initials, String time )
    {
        this.name = name;
        this.initials = initials;
        this.time = time;
    }
 
    public String getName()
    {
        return name;
    }
 
    public String getInitials()
    {
        return initials;
    }
 
    public String getTime()
    {
        return time;
    }
 
    ArrayList diffRecords = new ArrayList<Record>();
 
}

Now go through the assignment's description of a "record" and copy those descriptions as comments into your code. Something like:

/**
 * used to record each animal identified, including its name, the time of
 * its discovery, and the initials of the scientist who found it.
 */
public class Record
{
    // instance variables to store the animal's name, the initials of the
    // discovering scientist, and the time of discovery
    private String name;
    private String initials;
    private String time;
 
    // a constructor that sets name, scientist's initials, and time
    public Record ( String name, String initials, String time )
    {
        this.name = name;
        this.initials = initials;
        this.time = time;
 
    } // end constructor
 
// etc . . .

Your work has gotten much better! However, there is no reason for you to post "I think there are syntax errors." If there are, fix them. If you need help with them, post them, and ask for help. A collection of Records does not belong in the Record class.

Make any corrections/improvements to your class that you'd like and post the result. If questions occur to you, please ask them.

For extra Forum cred, show some initiative and try to do the next step on your own: create a driver class that collects the data and then creates and stores the data in Record instances.

Here's what I need help with. There's a separate code section to try out the solution. Here's my code for that. I'm getting a "cannot find symbol" error:

public static void main( String[] args )
 
{
 
 System.out.println("name is: " + name + ", time is: " + time);
 
 System.out.println("The scientist who discovered it was: " + initials);
 
}

You should know by now to post the error messages exactly as they appear to you, copied and pasted, not your interpretation or abbreviated version of them. Also, why isn't the new code you've posted indented or spaced properly?

Lol. My teacher saw my code and looked at it, including the driver class. He said the test area I could think of as my driver class.

 
public static void main( String[] args )
 
{
 
   // This is essentially a driver class
 
    ArrayList diffRecords = new ArrayList<Record>();
 
    diffRecords.add(new Record("Rhino", "JFK", "3:30"));
 
    diffRecords.add(new Record("Dino", "LBJ", "4:30"));
 
    diffRecords.add(new Record("Robot", "MF", "2:00"));
 
 
 
    for (Record a : diffRecords){
 
         System.out.println(a);
 
    }
 
}

--- Update ---

I hadn't even said much to him. He just looked at the class and said it was there.

I don't understand what you're saying. Is there a question in there? Or are you reporting success?