How to check programmatically if an application is installed or not in Android?

If the application is already installed in the device the application is open automatically.
Otherwise install the particular application.

    public class Example extends Activity {

1.     @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.main);
           //Put the package name here...
           boolean installed = appInstalledOrNot("com.Ch.Example.pack");  
           if(installed) {
               //This intent will help you to launch if the package is already installed
               Intent LaunchIntent = getPackageManager()
                   .getLaunchIntentForPackage("com.Ch.Example.pack");
               startActivity(LaunchIntent);
   
               System.out.println("App is already installed on your phone");         
           } else {
               System.out.println("App is not currently installed on your phone");
           }
       }
   
       private boolean appInstalledOrNot(String uri) {
           PackageManager pm = getPackageManager();
           boolean app_installed;
           try {
               pm.getPackageInfo(uri, PackageManager.GET_ACTIVITIES);
               app_installed = true;
           }
           catch (PackageManager.NameNotFoundException e) {
               app_installed = false;
           }
           return app_installed;
       }
   }