Taking a line from a text file if it contains the specified text

Hi Java developers,

I'm currently modding MineCraft (just for fun :)) and I'm stuck with a problem:
How do I copy a line of a .txt file which contains the specified text? (Hashset)

Example:

In my items.txt file:

Code:

---

cobblestone:4
smoothstone:1
sand:12
grass:2
water:8

---

In my code:

Code:

---

if (items.contains("cobblestone"))
{
    String blabla = //Code to copy cobble out of the .txt file;
    String[] k = blabla.split(":");
    int itemId = Integer.Parse(k[0]);
    player.dropPlayerItemWithoutDelay(new ItemStack(itemId, 64, 0), false);
}

---

So basically what I need to know is:
-How do I copy a specific line of .txt
-How do I get the line number of a .txt which contains a specific text

You could use a Scanner to load the file and parse through each line checking to see if "cobblestone" exists in each. And keep a counter to know how many lines you've gone through.