android - Which handler class to import? for webview twice backpress exit app -

i want go on app on 1 time press.. , if key presesd twice, want app exit. got following code on internet , stackoverflow.

@override     public void onbackpressed() {         if (doublebacktoexitpressedonce) {             super.onbackpressed();             return;         }          this.doublebacktoexitpressedonce = true;         toast.maketext(this, "please click again exit", toast.length_short).show();          new handler().postdelayed(new runnable() {              @override             public void run() {                 doublebacktoexitpressedonce=false;             }         }, 2000);     } 

now don't know handler class should imported here? either

`java.util.loggin.handler 

or

 `android.os.handler 

the second 1 (android.os.handler). can't explain more. 1 handler @ operating system level, , other used logging purposes (it's on package names, though)