Button to Clear just my apps cache

I have an app that loads up a lot of images and can become a hog on the memory I suppose. So I am trying to make it so the user can click a button to clear the cache of the app.

I have no idea how to do this but so far i have the button

Code (Text):

1.  
2. public class Clear extends Activity {
3.     protected void onCreate(Bundle icicle) {
4.         super.onCreate(icicle);
5.         setContentView(R.layout.clear);
6.  
7.         final Button trimCache = (Button) findViewById(R.id.trimCache);
8.         trimCache.setOnClickListener(new View.OnClickListener() {
9.             public void onClick(View v) {
10.                 //clear the cache here
11.             }
12.         });
13.     }
14. }
15.  

How would I go about making it clear only my apps cache?
Also as a little bonus can i make it so it sends like a back command so that it returns to the main part of the app since this "Clear" page is accessed via a menu?