title: What java rule "((CheckBox) v).isChecked())" use?
body: <p><code>CheckBox checkBox = (CheckBox) findViewById(R.id.chkAutosave);
      checkBox.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
          if (((CheckBox) v).isChecked())
            DisplayToast("CheckBox is checked");
          else
            DisplayToast("CheckBox is unchecked");
        }
      });</code></p>
  
  <p>What java rule does "((CheckBox) v)" use? 
  Is it shortening? how to deconstruct it?
  Are there some useful shortening except this one?</p>