MainActivity.java

/* Code From Learnoset - Learn Code Online Android App.*/
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// create an object of AlertDialog.Builder class
        AlertDialog.Builder alertDialog = new AlertDialog.Builder(MainActivity.this);

        // if setCancelable is true then dialog can be closed when user click outside the dialog
        alertDialog.setCancelable(false);

        // title of the dialog
        alertDialog.setTitle("Your Title Here");

        // message of the dialog
        alertDialog.setMessage("Your Message here");

        // set positive button / always appears on the bottom right corner with text (Right Btn)
        alertDialog.setPositiveButton("Right Btn", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {

                // handle click event on Right Btn like I'm showing Toast below
                Toast.makeText(MainActivity.this, "Right Button Clicked", Toast.LENGTH_SHORT).show();

                // use below code to hide the dialog on button click
                //dialog.dismiss();
            }
        });

        // set negative button / always appears to left of  positive button with text (Left Btn)
        alertDialog.setNegativeButton("Left Btn", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {

                // handle click event on Left Btn like I'm showing Toast below
                Toast.makeText(MainActivity.this, "Left Button Clicked", Toast.LENGTH_SHORT).show();

                // use below code to hide the dialog on button click
                //dialog.dismiss();
            }
        });

        // show alert dialog
        alertDialog.show();