type mismatch cannot convert from element type object to string

Question

I keep getting this error when making a search method in my code to search through string. I have gone through alot of examples trying to fix this but I cant find any. Thank you for any help and advise you can give.

public class runNote {

public static void main(String[] args) {
    // TODO Auto-generated method stub
    Notebook note = new Notebook();
    note.storeNote("happy");
    note.storeNote("hello there");
    note.storeNote("work at 5");
    note.storeNote("BBQ Time");
    note.storeNote("UNI!!!!");
    note.storeNote("Dont miss lecture at 9:15");
    System.out.println(note.numberOfNotes());
    note.showNote(1);
    note.searchNotes("hap");

}}




public class Notebook{


/**
 * Perform any initialization that is required for the
 * notebook.
 */
public Notebook()
{
    notes = new ArrayList();
}

/**
 * Store a new note into the notebook.
 * @param note The note to be stored.
 */
public void storeNote(String note)
{
    notes.add(note);
}

/**
 * @return The number of notes currently in the notebook.
 */
public int numberOfNotes()
{
    return notes.size();
}

/**
 * A simple search engine to find the correct notes.
 */
public void searchNotes(String search){ 
    for (String item : notes){
        if (item.contains(search)){
        System.out.println(item);
        }
    }
}

/**
 * Show a note.
 * @param noteNumber The number of the note to be shown.
 */
public void showNote(int noteNumber)
{
    if(noteNumber < 0) {
        // This is not a valid note number, so do nothing.
    }
    else if(noteNumber < numberOfNotes()) {
        // This is a valid note number, so we can print it.
        System.out.println(notes.get(noteNumber));
    }
    else {
        // This is not a valid note number, so do nothing.
    }
}
}

Paste the exact and complete error message, and tell us which line it refers to. — JB Nizet
– JB Nizet, Commented Dec 7, 2013 at 19:16
Where is the declaration for notes? Are you declaring it as ArrayList when you should declare it as ArrayList<String>? — Code-Apprentice
– Code-Apprentice, Commented Dec 7, 2013 at 19:24
Error: Exception in thread "main" java.lang.Error: Unresolved compilation problem: Type mismatch: cannot convert from element type Object to String at lab8.Notebook.searchNotes(Notebook.java:47) at lab8.runNote.main(runNote.java:16) — user202051
– user202051, Commented Dec 7, 2013 at 19:37
The declaration for notes is in the public Notebook() { notes = new ArrayList(); } — user202051
– user202051, Commented Dec 7, 2013 at 19:37

Sage · Accepted Answer · 2013-12-07 19:19:00Z

5

You are having exception at this line :

 for (String item : notes)

notes is an ArrayList declared as raw type, although i don't see the declaration i can see this line of initialization:

notes = new ArrayList();

which sees it's element as of type Object You need to declare notes with ArrayList<String> type such as:

  ArrayList<String> notes = new ArrayList<>();

answered Dec 7, 2013 at 19:19

Sage

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2 Comments

user202051 Over a year ago

If I change the declaration I get this error: Exception in thread "main" java.lang.NullPointerException at lab8.Notebook.storeNote(Notebook.java:32) at lab8.runNote.main(runNote.java:8)

Sage Over a year ago

have you initialized notes list as i described above ?

openmike · Accepted Answer · 2013-12-07 19:17:21Z

4

Add notes as a global variable to your class

public class Notebook{
ArrayList<String> notes = null;

....
}

In the constructor, do:

public Notebook()
{
    notes = new ArrayList<String>();
}

answered Dec 7, 2013 at 19:17

openmike

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4 Comments

Code-Apprentice Over a year ago

This is a member variable, not a global one.

openmike Over a year ago

That is a default constructor

hrv Over a year ago

In Java 7, you don't need to specify String type with the new

Sage Over a year ago

@Code-Guru, thank you, in fact complete different exception :) ;)

Palejandro · Accepted Answer · 2013-12-07 19:20:13Z

0

try this: notes = new ArrayList<String>();

answered Dec 7, 2013 at 19:20

Palejandro

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Comments

hrv · Accepted Answer · 2013-12-07 19:23:07Z

0

You don't declare the notes variable

public class Notebook{
  private ArrayList<String> notes;
...

answered Dec 7, 2013 at 19:23

hrv

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