Have some methods to set up for some Java HW that I'm having trouble with.

[zac woot]

Was given this interface to implement.

public interface SetInterface {
/** <code>add</code> will add the parameter to the set, unless
	it is already there, in which case it returns false
	@param dbl is the Double to add
	@return true if added, false if not
*/
public boolean add(Double dbl);
/** <code>remove</code> will remove the parameter from the set,
	unless it is not there, in which case it returns false
	@param dbl is the Double to remove
	@return true if removed, false if not
*/
public boolean remove(Double dbl);
/** <code>contains</code> will return true if the parameter is
	in the set, else false
	@param dbl is the Double to test
	@return true if dbl is in the set, false if not
*/
public boolean contains(Double dbl);
/** <code>empty</code> will return true if the set is empty, else false
	@return true if the set is empty, false if not
*/
public boolean empty();
/** <code>size</code> will return the cardinality of the set
	@return the number of elements in the set
*/
public int size();
}

So far have made

import java.util.ArrayList;

public class Set implements SetInterface {

	private ArrayList<Double> a;
	
	public Set(){
		a = new ArrayList<Double>();
	}
	
	
	/** <code>add</code> will add the parameter to the set, unless
	it is already there, in which case it returns false
	@param dbl is the Double to add
	@return true if added, false if not
    */
	public boolean add(Double dbl) {
		a.add(dbl);
		if(dbl<0){
			throw new IllegalArgumentException("Error - add input is not a double.");	
		}
		if(a.contains(dbl)){
			return false;
		}
		return true;	
	}

	
	/** <code>remove</code> will remove the parameter from the set,
	unless it is not there, in which case it returns false
	@param dbl is the Double to remove
	@return true if removed, false if not
    */
	public boolean remove(Double dbl) {
		
                  return false;
	}

	
	/** <code>contains</code> will return true if the parameter is
	in the set, else false
	@param dbl is the Double to test
	@return true if dbl is in the set, false if not
    */
	public boolean contains(Double dbl) {
		
		return false;
	}

	
	/** <code>empty</code> will return true if the set is empty, else false
	@return true if the set is empty, false if not
    */
	public boolean empty() {
		
		return false;
	}

	
	/** <code>size</code> will return the cardinality of the set
	@return the number of elements in the set
    */
	public int size() {
		
		return 0;
	}

	
	@Override
	public String toString() {
	    String result = "";
	    for (int i = 0; i < a.size(); i++) {
	        result += " " + a.get(i);
	    }
	    return result;
	}
	
	
}

Also made a driver class which makes a Set and adds 3 elements to it and prints them. I'm having trouble with remove and contains methods. I'm also supposed to have an override equals to method and toString method, and I've already done the toString one.

[Liutauras Vilda]

Hi,

Have a look at > HowToAskQuestionsOnJavaRanch, you might find this useful.

zac woot wrote:I'm having trouble with remove and contains methods.

Please be more precise what kind of troubles you facing?

And is worth to check how properly UseCodeTags

[Knute Snortum]

I've put in the code tags for you this time.

There's nothing illegal about a double being negative.

[zac woot]

Ok thanks for the replies I see what I did wrong with the code text. Thanks for the comment on the doubles being negative, we were instructed to not allow negatives in the list for some reason and I just auto pilot typed that ha.

Solved all the methods just now. I'm not as rusty as I thought I was apparently.