How to remove an element from a String array?

Question

I have an array which contains three items, for example:

title_list = new String[] { title1, title2, title3 };

These values are coming from SharedPreferences. I would like to check so that if any of these values are empty they should be removed from the array.

For example, if the value of title1 is coming from another activity and is null, then title1 should be removed and the array will be String[] { title2, title3 }.

Here is my code:

package com.example.e_services;

import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;

public class FavList extends Activity {
    // Declare Variables
    ListView list;
    FavListViewAdapter adapter;
    String[] rank;
    String[] link;
    String[] population;
    String title1, title2;
    String link1, link2;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // Get the view from listview_main.xml
        setContentView(R.layout.listview_main2);

        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());

        title1 = prefs.getString("title1", ""); //no id: default value
        title2 = prefs.getString("title2", ""); //no id: default value

        link1 = prefs.getString("link1", ""); //no id: default value
        link2 = prefs.getString("link2", ""); //no id: default value

        if (title1.length() == 0){
            rank[0] = null;             
        }

        // Generate sample data into string arrays
        rank = new String[] { title1, title2, "title3" };
        link = new String[] { link1, link2 };

        // Locate the ListView in listview_main.xml
        list = (ListView) findViewById(R.id.listview);

        // Pass results to ListViewAdapter Class
        adapter = new FavListViewAdapter(this, rank);
        // Binds the Adapter to the ListView
        list.setAdapter(adapter);
        // Capture ListView item click
        list.setOnItemClickListener(new OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Intent i = new Intent(FavList.this, WebsiteView.class);
                // Pass all data rank
                i.putExtra("Link", link);
                i.putExtra("position", position);
                //Toast.makeText(getBaseContext(), "link  "+link1,Toast.LENGTH_SHORT).show();
                startActivity(i);
            }
        });
    }
}

I tried to use

if (title1.length() == 0 ){
    title_list[0] = null;               
}

but it did not work.

You can't remove an element from an array, it has a fixed size. You will have to create a new, smaller array, and copy the elements you want. — Keppil
– Keppil, Commented Oct 5, 2014 at 19:47
@Keppil why the op cannot remove any element from an array. the only thing that op has to do, to shift other existing elements forward or backward depened on the index of deleted array — Kick Buttowski
– Kick Buttowski, Commented Oct 5, 2014 at 19:50
Saying "it did not work" doesn't tell us anything about what you expected to happen or what actually happened. — Jon Skeet
– Jon Skeet, Commented Oct 5, 2014 at 20:05

Jon Skeet · Accepted Answer · 2014-10-05 19:48:01Z

3

You can't remove an element from an existing array - once you have created an array, its length is fixed. You can replace elements, but you can't add or remove them.

Options:

Change the value of the variable to refer to a new list, e.g.

title_list = new String[] { title_list[1], title_list[2] };

Use a List<String> instead, using something like an ArrayList<String> as the implementation

answered Oct 5, 2014 at 19:48

Jon Skeet

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3 Comments

Kick Buttowski Over a year ago

why the op cannot remove any element from an array. the only thing that op has to do, to shift other existing elements forward or backward depened on the index of deleted array

Jon Skeet Over a year ago

@KickButtowski: "Remove" suggests that the length of the array will change. Shifting the elements backwards or forwards won't do that. You can't remove an element in an array, because its size is fixed. If the OP is fine keeping a 3-element array where only two of the elements are "useful", that's fine... but it's not removing the element.

Jon Skeet Over a year ago

@KickButtowski: In particular, the OP said in the question: "and the array will be String[] {title2, title3}" - that won't be the case if elements are just replaced within a 3-element array.

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