The size of the content will be the same as that of its ScrollPane container.
import javafx.scene.control.ScrollPane; //Import the ScrollPane
import javafx.scene.control.ScrollPane.ScrollBarPolicy; //Import the ScrollBarPolicy
import javafx.scene.layout.Pane;
ScrollPane scrollpane;
Pane content = new Pane(); //We will use this Pane as a content
scrollpane = new ScrollPane(content); //Initialize and add content as a parameter
scrollpane.setPrefSize(300, 300); //Initialize the size of the ScrollPane
scrollpane.setFitToWidth(true); //Adapt the content to the width of ScrollPane
scrollpane.setFitToHeight(true); //Adapt the content to the height of ScrollPane
scrollpane.setHbarPolicy(ScrollBarPolicy.ALWAYS); //Control the visibility of the Horizontal ScrollBar
scrollpane.setVbarPolicy(ScrollBarPolicy.NEVER); //Control the visibility of the Vertical ScrollBar
//There are three types of visibility (ALWAYS/AS_NEEDED/NEVER)