Android AlertDialog Single Button

You could use this:

AlertDialog.Builder builder1 = new AlertDialog.Builder(this);
builder1.setTitle("Title");
builder1.setMessage("my message");
builder1.setCancelable(true);
builder1.setNeutralButton(android.R.string.ok,
        new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int id) {
        dialog.cancel();
    }
});

AlertDialog alert11 = builder1.create();
alert11.show();

Another approach

Builder alert = new AlertDialog.Builder(ActivityName.this);
alert.setTitle("Doctor");
alert.setMessage("message");
alert.setPositiveButton("OK",null);
alert.show(); 

Bonus

AlertDialog.Builder builder = new AlertDialog.Builder(YourActivityName.this);
builder.setMessage("Message dialog with three buttons");

       builder.setPositiveButton("YES", new DialogInterface.OnClickListener() {
           public void onClick(DialogInterface dialog, int id) {
                //do things
           }
       });

      builder.setNegativeButton("NO", new DialogInterface.OnClickListener() {
           public void onClick(DialogInterface dialog, int id) {
                //do things
           }
       });

       builder.setNeutralButton("CANCEL", new DialogInterface.OnClickListener()     {
           public void onClick(DialogInterface dialog, int id) {
                //do things
           }
       });
AlertDialog alert = builder.create();
alert.show();

Now it is up to you to use one,two or three buttons..

Couldn't that just be done by only using a positive button?

AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("Look at this dialog!")
       .setCancelable(false)
       .setPositiveButton("OK", new DialogInterface.OnClickListener() {
           public void onClick(DialogInterface dialog, int id) {
                //do things
           }
       });
AlertDialog alert = builder.create();
alert.show();

This is the closer I could get to the one liner this should be if the Android API was any smart:

new AlertDialog.Builder(this)
    .setMessage(msg)
    .setPositiveButton("OK", null)
    .show();