There are two ways to set a tool tip on a tab. The first is to specify it when the tab is created; the second way is to set it using JTabbedPane.setToolTipTextAt().

    // Create a tabbed pane

    JTabbedPane pane = new JTabbedPane();

    // Add a tab with a tool tip

    String label = "Tab Label";

    String tooltip = "Tool Tip Text";

    pane.addTab(label, null, component, tooltip);

    // Get index of new tab

    int index = pane.getTabCount()-1;

    // Get current tool tip

    tooltip = pane.getToolTipTextAt(index);

    // Change tool tip

    tooltip = "New Tool Tip Text";

    pane.setToolTipTextAt(index, tooltip);