下面我推荐这种方式：

public static void main(String[] args) {
        double test1=10.2234;
        double test2=10.3356;
        double test3=10.0000;
        String testStr1 = String.format("%.2f", test1);
        String testStr2 = String.format("%.2f", test2);
        String testStr3 = String.format("%.2f", test3);
        System.out.println("String类型：");
        System.out.println(testStr1);
        System.out.println(testStr2);
        System.out.println(testStr3);

        Double dtest1 = Double.valueOf(String.format("%.2f", test1 ));
        Double dtest2 = Double.valueOf(String.format("%.2f", test2 ));
        Double dtest3 = Double.valueOf(String.format("%.2f", test3 ));

        System.out.println("Double类型：");
        System.out.println(dtest1 );
        System.out.println(dtest2 );
        System.out.println(dtest3 );
    }

结果（四舍五入保留2位）：