This tutorial explains how to build and show an AlertDialogue in android java. some example code is also added in the tutorial, you can use the code in your project to experiment with the code

What is an AlertDialogue?

AlertDialogue is a small popup message window that can be used to show message alerts to alert user about something. below is an alertdialogue example

This is an alertdialogue, with 3 buttons

You can use alertdialogue to alert a user about something, such as – asking to exit an app, show a temporary message alert etc

Here is an alertdialogue example java code, you can change the title, message and actions as you wish. In this code, this will show just a toast when you click on the buttons. instead of toast, you can set actions also as you like

AlertDialog.Builder builder = new AlertDialog.Builder(this, R.style.MyAlertDialogTheme);
           builder.setTitle("This is a title"); 
           builder.setMessage(" This is message,you can change this message");
           builder.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
               @Override
               public void onClick(DialogInterface dialog, int which) {
                   Toast.makeText(getApplicationContext(), "Ok button clicked..",
                   Toast.LENGTH_LONG).show();
               }
           });
           builder.setNegativeButton("Cancel", null);
           builder.setNeutralButton("Neutral button", new DialogInterface.OnClickListener() {
               @Override
               public void onClick(DialogInterface dialog, int which) {
                   Toast.makeText(getApplicationContext(), "Neutral button button clicked..",
                   Toast.LENGTH_LONG).show();
               }
           });

           builder.show();

This code will display an alertdialogue with 3 buttons, you can define actions to all this buttons. you can change the theme of an alertdialogue also by creating a theme in the Styles if you want, creating a custom theme for alert dialogue is explained in this site.