https://docs.oracle.com/javase/jp/18/docs/api/java.desktop/javax/swing/plaf/basic/BasicBorders.SplitPaneBorder.html
BasicBorders.SplitPaneBorder (Java SE 18 & JDK 18)
declaration: module: java.desktop, package: javax.swing.plaf.basic, class: BasicBorders, class: SplitPaneBorder
java sejdk