Call String Value To URL In Android

I have develop one android application. Here i have to pass string value to url. How can i pass the string value to url.give me solution for these.

[HIGH]
String mTitle;
String URL = "http://api1.sfsfsffsf.com/dev/categories/?fields=&categoryid=" + mTitle + "&access_token=bfb787a";
static String KEY_CATEGORY = "category";
// public static final String URL_Address=null;

[Code]...

This is my url: [URL]....I have mentioned directly **categoryid=10** means have displayed all product.

But I have to change this url like:

[URL]....

Nw i have changed my url like categoryid="+mTitle+" means not displayed all products.

mTitle value is getting from my previous activity.

whats wrong in my code.

my mTitle value is 10.i have to wrote the code like means

[HIGH]
grandtotal.setText("Welcome ," + mTitle );[/HIGH]its displayed mTitle value successfully.

[HIGH]grandtotal.setText("Welcome ," + URL );[/HIGH]means gave me null value