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

The above code didn't work for me. The following approach worked.

Create an Intent object with appropriate info and then check if the Intent is callable or not using the following function:

private boolean isCallable(Intent intent) {  
        List<ResolveInfo> list = getPackageManager().queryIntentActivities(intent,   
        PackageManager.MATCH_DEFAULT_ONLY);  
        return list.size() > 0;  
}

Try with this:

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Add respective layout
        setContentView(R.layout.main_activity);

        // Use package name which we want to check
        boolean isAppInstalled = appInstalledOrNot("com.check.application");  
        
        if(isAppInstalled) {
            //This intent will help you to launch if the package is already installed
            Intent LaunchIntent = getPackageManager()
                .getLaunchIntentForPackage("com.check.application");
            startActivity(LaunchIntent);
                    
            Log.i("SampleLog", "Application is already installed.");          
        } else {
            // Do whatever we want to do if application not installed
            // For example, Redirect to play store

            Log.i("SampleLog", "Application is not currently installed.");
        }
    }

    private boolean appInstalledOrNot(String uri) {
        PackageManager pm = getPackageManager();
        try {
            pm.getPackageInfo(uri, PackageManager.GET_ACTIVITIES);
            return true;
        } catch (PackageManager.NameNotFoundException e) {
        }

        return false;
    }

}

Somewhat cleaner solution than the accepted answer (based on this question):

public static boolean isAppInstalled(Context context, String packageName) {
    try {
        context.getPackageManager().getApplicationInfo(packageName, 0);
        return true;
    }
    catch (PackageManager.NameNotFoundException e) {
        return false;
    }
}

I chose to put it in a helper class as a static utility. Usage example:

boolean whatsappFound = AndroidUtils.isAppInstalled(context, "com.whatsapp");

This answer shows how to get the app from the Play Store if the app is missing, though care needs to be taken on devices that don't have the Play Store.