JSplitPane

JSplitPane is a Swing container that renders two components separated by a draggable divider. It is commonly used to create editors and views where the user can adjust how much space is allotted to each pane. The pane can be oriented horizontally or vertically, corresponding to a left–right or top–bottom arrangement.

Two components can be supplied up front via a constructor or later through setter methods. When horizontal, the components are positioned as left and right; when vertical, as top and bottom. Accessors exist for each side: setLeftComponent/setRightComponent and setTopComponent/setBottomComponent.

Key properties include the divider location, divider size, continuous layout, and resize weight. The divider location can be set programmatically with setDividerLocation(int) or as a proportional value with setDividerLocation(double). The divider size is setDividerSize. If continuousLayout is true, dragging the divider continuously reparses layout; if false, layout occurs after the drag ends. resizeWeight controls how extra space is allocated to the two components when the split pane itself is resized: a value of 0.0 prioritizes one side, while higher values distribute space more evenly.

JSplitPane fires property change events for changes such as dividerLocation and orientation, enabling listeners to respond to user adjustments.

Constructors include: new JSplitPane(int orientation), new JSplitPane(int orientation, Component left, Component right), and equivalent variants for vertical orientation using top and bottom semantics.

Usage typically involves adding the split pane to a container with a layout manager (for example, in the center of a frame). It can host any Swing components, making it a versatile tool for creating resizable, dual-pane interfaces.