Question

I am creating a demo shopping cart in android for this i am using Application class for saving data. I am unable to delete data from linkedlist. I am calling removeItem() function for android activity for removing selected item from the list but it is not working any one can help me.

    package in.co.santoshsharma.bookshopping;

import java.util.LinkedList;

import android.app.Application;
import android.content.res.Configuration;

public class GlobalData extends Application{
    private String email;
    private String itemName;
    private int itemQuantity;
    private int itemCost;

    public GlobalData(){

    }
    public  GlobalData(String iName,int iQunt,int iCost) {
        // TODO Auto-generated constructor stub
        this.itemCost=iCost;
        this.itemName=iName;
        this.itemQuantity=iQunt;

    }




    public void setEmail(String mail)
    {
        this.email=mail;
    }

    public String getEmail()
    {
        return email;
    }
    public String getItemName()
    {
        return itemName;
    }

    public int getItemCost()
    {
        return itemCost;
    }

    public int getItemQunt()
    {
        return itemQuantity;
    }



    LinkedList<GlobalData> list = new LinkedList<GlobalData>();

    public void setList(String iName,int iQunt,int iCost)
    {
        list.add(new GlobalData( iName, iQunt, iCost));
    }

    public LinkedList<GlobalData> getList()
    {
        return list;
    }
    public void removeItem(String iName,int iQunt,int iCost)
    {
        for(GlobalData data:list)
        {
            if(data.getItemName().equals(iName))
            {
                list.remove(itemName);
                //list.remove(iCost);
                //list.remove(iQunt);
            }
        }
    } 



}

Answer 1

First, override equals() method and use itemName attribute for the comparison

@Override
public boolean equals(Object o) {
  if (o == null) return false;
  if (itemName == null) return false;
  if (o instanceOf String) return itemName.equals(o);
  else if (o instanceOf GlobalData) return ((GlobalData) o).itemName.equals(this.itemName);
  else return false;
}

Then, change your removeItem() method

public void removeItem(String iName) {
  list.remove(iName);
  // or uncomment line below to completely remove all matching elements
  // for (;;list.remove(iName)) {}
}

According to http://docs.oracle.com/javase/6/docs/api/java/util/LinkedList.html#remove(java.lang.Object) remove() method of a LinkedList will call the equals() method of the supplied Object and compare it with every element in the list.

Hope this helps 🙂