java EnumSet

 enum FrontConstant{plain,bold,italic}
    public static void main(String[] args) {

        EnumSet<FrontConstant> es=EnumSet.of(FrontConstant.plain);//#14
        Iterator it=es.iterator();

        System.out.println("17");
        while (it.hasNext())
            System.out.println(it.next());//es初始化了一个元素plain 输出plain
        System.out.println("20");

        System.out.println("22");
        System.out.println(EnumSet.complementOf(es));//#14是plain 剩下bold和italic 输出{bold，italic}
        System.out.println("24");

        EnumSet<FrontConstant> es2=EnumSet.noneOf(FrontConstant.class);
        es2.add(FrontConstant.plain);//#27
        System.out.println("28");
        System.out.println(EnumSet.complementOf(es2));//#27是plain 剩下bold和italic 输出{bold，italic}
        System.out.println("30");

        ArrayList<FrontConstant> a1=new ArrayList<FrontConstant>();
        a1.add(FrontConstant.plain);
        a1.add(FrontConstant.italic);

        EnumSet<FrontConstant> es3=EnumSet.copyOf(a1);
        System.out.println("37");
        System.out.println(EnumSet.complementOf(es3)); //es3初始化后已经包含 plain和italic 剩下bold输出bold
        System.out.println("39");
       
        }