Java数组索引超出范围异常：-1

Question

Alright , I have a problem which I can't figure out whats wrong. So I have jList and List . I need a function that when I click on item (in jList any item ) and it would change in my label icon , (I'm dealing with images). It works somehow, it changes my label icon to the image I pick from jList, but it throws me Exception and the program crashes , usually first 2 items cause no errors , third and further items cause it. After it crashes and throws me bunch of red text , I can still change my icon.

This is the function where I get the images and add them to List (adding path to them)

private static void getImages(String src) throws IOException {
    //Exctract the name of the image from the src attribute
    int indexname = src.lastIndexOf("/");

    if (indexname == src.length()) {
        src = src.substring(1, indexname);
    }

    indexname = src.lastIndexOf("/");
    String name = src.substring(indexname, src.length());

    //Open a URL Stream
    URL url = new URL(src);
    InputStream in = url.openStream();

    GPath=fPath+name;
    OutputStream out = new BufferedOutputStream(new FileOutputStream( GPath));
    //Im adding to the list string (link to image) here
    imagesListN.add(GPath);

    System.out.println("list size: "+imagesListN.size());


    for (int b; (b = in.read()) != -1;) {

        out.write(b);
    }

    out.close();
    in.close();

}

It adds them normally . Yes I'm downloading them , that's why I want to see them once they are downloaded.

This is where I click on jList function.

     list.addListSelectionListener(new ListSelectionListener() {

        private int a;

        @Override
        public void valueChanged(ListSelectionEvent arg0) {
            if (!arg0.getValueIsAdjusting()) {
                String h;
                int k;
                k = list.getSelectedIndex();
                System.out.println("List id: "+k);
                a = Main.imagesListN.indexOf(k);
                System.out.println("imagesListN id: "+a);

                h = Main.imagesListN.get(k);
                System.out.println("h : "+h);
                ImageIcon img = new ImageIcon(h);

                imageReview.setIcon(img);
                try {
                    Thread.sleep(50);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
    });

Here is the jList (name list) . Exception is at

a = Main.imagesListN.indexOf(k);

it gives me -1 , but the h = Main.imagesListN.get(k); gives me the link I need and gives it to ImageIcon img = new ImageIcon(h); and then imageReview.setIcon(img); . Label icon changes everytime when I click on item I need. Maybe it's not a = Main.imagesListN.indexOf(k); that I'm looking at , but something gives me -1. Btw I'm excecuting everything in Thread.

`public class Crawler extends Thread {

Main main = new Main();

public void run(){
        try {
                main.download();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

}`

nothing fancy here. Each functions are in there own class , getImages() is in main , listListener is in class Langas (Class where are all buttons,labels , etc. are created nothing else) and Thread well , Thread. Also it works fine after everything is downloaded , no exceptions . Error appears durring downloading proccess

Answer 1

indexOf api accepts Object as parameter, while get accepts Object as well as primitive types. So when you call get with primitive type element, it looks for element by an index which you may have found.

But when you do indexOf, you are searching for an object within your list and hence you get -1.