Pfthb

I'm new to Java and I am trying to write a description class that will return an array of strings from calling describe through my interface.

this line: return Collections.toString(items); is throwing the error in the title, and I can't understand why.

I know that I need to return type string and that items are not currently a string but I'm new to Java and not sure what to change.

trace error when run: java.lang.Error: Unresolved compilation problem:
The return type is incompatible with Describe.describe()

package uk.ac.uos.assignment;

import java.util.*; 

public class Description implements Describe 
 private Collection<Describe> items;

 public Description() 
 this.items = new ArrayList<>();
 

 public String describe() 
 return Collections.toString(items);
 

 public void add(Describe d) 
 items.add(d); 
 

and this is my interface:

package uk.ac.uos.assignment;

interface Describe 

 String describe();

Now, in the "describe()" method, I would suggest you do the following:

1) Create an empty String;

2) Iterate through the Collection and add every element, as a string, to the empty string you have created;

3) Return the String.

The basic algorithm I described above, now here's somewhat of an implementation:

public String describe()

 StringBuilder y = new StringBuilder();
 items.forEach(i -> y.append(i.toString()));

 return y.toString();

Note: For this to work, your project must be set to use Java 8 or newer. If it is not, you will need to do a classical iteration through the Collection and then append each element to the StringBuilder.

Note 2: Your "Description" class must have its "toString()" method implemented. Before implementing it though, you should use an @Override annotation, just above the method:

@Override
public String toString()...

What I understand is that you want a String array returning the String representation of each of those items in your Collection<Describe> items.

Iterate over the collection and call the toString() method of every Describe item provided that the Describe class has its own implementation of toString.

This would get you a String for each of those items in your collection, collect them and return at the end.

public String describe() 
 List<String> descriptions = new ArrayList<String>(items.size());
 for(Describe item: items) 
 descriptions.add(item.toString());
 
 return descriptions.toArray(new String[items.size()]);