import apple.laf.JRSUIConstants.AlignmentHorizontal; //导入依赖的package包/类
public static UIResource getTreeExpandedIcon() {
    // public, because UIDefaults.ProxyLazyValue uses reflection to get this value
    return AquaIcon.getIconFor(new JRSUIControlSpec() {
        public void initIconPainter(final AquaPainter<? extends JRSUIState> painter) {
            painter.state.set(Widget.DISCLOSURE_TRIANGLE);
            painter.state.set(State.ACTIVE);
            painter.state.set(Direction.DOWN);
            painter.state.set(AlignmentHorizontal.CENTER);
            painter.state.set(AlignmentVertical.CENTER);
        }
    }, 20, 20);
}
 

import apple.laf.JRSUIConstants.AlignmentHorizontal; //导入依赖的package包/类
public static UIResource getTreeCollapsedIcon() {
    // public, because UIDefaults.ProxyLazyValue uses reflection to get this value
    return AquaIcon.getIconFor(new JRSUIControlSpec() {
        public void initIconPainter(final AquaPainter<? extends JRSUIState> painter) {
            painter.state.set(Widget.DISCLOSURE_TRIANGLE);
            painter.state.set(State.ACTIVE);
            painter.state.set(Direction.RIGHT);
            painter.state.set(AlignmentHorizontal.CENTER);
            painter.state.set(AlignmentVertical.CENTER);
        }
    }, 20, 20);
}
 

import apple.laf.JRSUIConstants.AlignmentHorizontal; //导入依赖的package包/类
public static UIResource getTreeRightToLeftCollapsedIcon() {
    // public, because UIDefaults.ProxyLazyValue uses reflection to get this value
    return AquaIcon.getIconFor(new JRSUIControlSpec() {
        public void initIconPainter(final AquaPainter<? extends JRSUIState> painter) {
            painter.state.set(Widget.DISCLOSURE_TRIANGLE);
            painter.state.set(State.ACTIVE);
            painter.state.set(Direction.LEFT);
            painter.state.set(AlignmentHorizontal.CENTER);
            painter.state.set(AlignmentVertical.CENTER);
        }
    }, 20, 20);
}