Functional Interfaces turn this:
glfwSetFramebufferSizeCallback(window, (framebufferSizeCallback = new GLFWFramebufferSizeCallback() {

	@Override
	public void invoke(long window, int width, int height) {
		onResize(width, height);
	}
}));

Into this:
glfwSetFramebufferSizeCallback(window, (framebufferSizeCallback = GLFWFramebufferSizeCallback.create(this::onResize)));