Android : when i am selecting only one checkbox then , why other checkboxes select autometically in expandablelistview in android

package com.myhotel;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.List;
import java.util.Map;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseExpandableListAdapter;
import android.widget.CheckBox;
import android.widget.ExpandableListView.OnChildClickListener;
import android.widget.TextView;

public class CustomOrderEListAdapter extends BaseExpandableListAdapter {
Context context;
ArrayList<String> hotelsRecipeList;
HashMap<String, List<String>> hotelsRecipeItemList;

public CustomOrderEListAdapter(OrderActivity orderActivity,
        ArrayList<String> hotelsRecipeList,
        HashMap<String, List<String>> hotelsRecipeItemList) {
    this.context = orderActivity;
    this.hotelsRecipeList = hotelsRecipeList;
    this.hotelsRecipeItemList = hotelsRecipeItemList;
}

@Override
public Object getChild(int groupPosition, int childPosition) {
    return hotelsRecipeItemList.get(hotelsRecipeList.get(groupPosition))
            .get(childPosition);
}

@Override
public long getChildId(int groupPosition, int childPosition) {

    return childPosition;
}


//this Map is used for storing checkbox object for checking purpose
Map<String, CheckBox> chkMap=new Hashtable<String, CheckBox>();

@Override
public View getChildView(int groupPosition, int childPosition,boolean isLastChild, View         convertView, ViewGroup parent)
{
    String childText = (String) getChild(groupPosition, childPosition);
    if (convertView == null)
    {
        LayoutInflater inflater = (LayoutInflater)    context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = inflater.inflate(R.layout.list_child, null);

    }

        TextView textOrderChildItemName = (TextView) convertView.findViewById(R.id.textOrderChildItemName);
        CheckBox chkOrderItem = (CheckBox) convertView.findViewById(R.id.chkOrderItem);

        chkMap.put(groupPosition+","+childPosition, chkOrderItem);
        textOrderChildItemName.setText(childText);




    //Toast.makeText(context, "size"+chkMap.size(),Toast.LENGTH_LONG).show();
    return convertView;
}

@Override
public int getChildrenCount(int groupPosition) 
{
    return hotelsRecipeItemList.get(hotelsRecipeList.get(groupPosition)).size();
}

@Override
public Object getGroup(int groupPosition) 
{
    return hotelsRecipeList.get(groupPosition);
}

@Override
public int getGroupCount() 
{
    return hotelsRecipeList.size();
}

@Override
public long getGroupId(int groupPosition)
{
    return groupPosition;
}

@Override
public View getGroupView(int groupPosition, boolean isExpanded,View convertView, ViewGroup parent) 
{

    String groupText = (String) getGroup(groupPosition);
    if (convertView == null) 
    {
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = inflater.inflate(R.layout.list_group, null);
    }
    TextView textOrderRecipeName = (TextView) convertView.findViewById(R.id.textOrderRecipeName);
    textOrderRecipeName.setText(groupText);
    //Toast.makeText(context, "size"+chkMap.size(),Toast.LENGTH_LONG).show();
    return convertView;
}

@Override
public boolean hasStableIds()
{
    return false;
}
@Override
public boolean isChildSelectable(int groupPosition, int childPosition)
{
    CheckBox chk=(CheckBox) chkMap.get(groupPosition+","+childPosition);
    if(chk.isChecked())
    {
        chk.setChecked(false);
        //Toast.makeText(context, "false",Toast.LENGTH_LONG).show();
    }
    else
    {
        chk.setChecked(true);
        //Toast.makeText(context, "true",Toast.LENGTH_LONG).show();
    }
    //Toast.makeText(context, "group- >"+groupPosition+"child=>"+childPosition,Toast.LENGTH_LONG).show();
    return true;
}

}

hello friends ,i have added one textview and one check box as a child row in expandablelistview i when am selecting only one checkbox in expandablelistview then other checkbox automatically selecting , which are i don't want to select, i mean when i select any particular chaeckbox that only should be selecting, please help me. thanks in advance