Add the jpushover dependency to your pom.xml:
de.svenkubiak jpushover x.x.x
Use the JPushover object with the required informations were you want

JPushover.newMessage() .withToken("MyToken") .withUser("MyUser") .withMessage("MyMessage") .push();

JPushover.newGlance() .withToken("MyToken") .withUser("MyUser") .withText("MyText") .push();

When using the Message API you can additionally add available options from the official Pushover documentation

You can also validate a user and token using the following method

boolean valid = JPushover.newMessage()
	.withToken("MyToken")
	.withUser("MyUser")
	.validate();

If you want more information and/or the response from the Pushover API, use the JPushoverResponse object.

JPushoverResponse jPushoverResponse = JPushover.newMessage()
	.withToken("MyToken")
	.withUser("MyUser")
	.withMessage("MyMessage")
	.push();

The JPushoverResponse will return the raw HTTP status code, along with the raw JSON response and a convenient boolean if the request was successful or not.