type mismatch cannot convert from element type object to string

问题

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.
    }
}
}

回答1:

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>();
}

回答2:

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<>();

回答3:

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

回答4:

You don't declare the notes variable

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

来源：https://stackoverflow.com/questions/20445428/type-mismatch-cannot-convert-from-element-type-object-to-string

标签

java

string

object

mismatch