12条通用编程原则✨全面提升Java编码规范性、可读性及性能表现

        //for循环局部变量作用域只在循环中
        for (Iterator iterator = list.iterator(); iterator.hasNext(); ) {
            System.out.println(iterator.next());
        }

        //while循环作用域更大
        Iterator<Integer> i1 = list.iterator();
        while (i1.hasNext()) {
            System.out.println(i1.next());
        }

        Iterator<Integer> i1 = list.iterator();
        while (i1.hasNext()) {
            System.out.println(i1.next());
        }

        Iterator<Integer> i2 = list.iterator();
        //CV大法忘记修改 i1
        while (i1.hasNext()) {
            System.out.println(i1.next());
        }

        List<Integer> list = Arrays.asList(1, 2, 3, 4, 5, 6);
        //for循环
        for (Iterator iterator = list.iterator(); iterator.hasNext(); ) {
            System.out.println(iterator.next());
        }
        for (int index = 0; index < list.size(); index++) {
            System.out.println(list.get(index));
        }

        //foreach
        for (Integer integer : list) {
            System.out.println(integer);
        }

        //拥有的钱 1.00
        double funds = 1.00;
        int itemsBought = 0;
        //每次都买商品递增 0.1
        //每次价格 0.1、0.2、0.3、0.4 期望买四个商品 剩下的钱为0
        for (double price = 0.10; funds >= price; price += 0.10) {
            funds -= price;
            itemsBought++;
        }
        //3 items bought.
        System.out.println(itemsBought + " items bought.");
        //Change: $0.3999999999999999
        System.out.println("Change: $" + funds);

        //去除小数、使用整形
        int funds = 100;
        int itemsBought = 0;
        for (int price = 10; funds >= price; price += 10) {
            funds -= price;
            itemsBought++;
        }
        //4 items bought.
        System.out.println(itemsBought + " items bought.");
        //Cash left over: 0 cents
        System.out.println("Cash left over: " + funds + " cents");

       Comparator<Integer> naturalOrder = (i, j) -> (i < j) ? -1 : (i == j ? 0 : 1);
       int result1 = naturalOrder.compare(new Integer(42), new Integer(42));
       // 1
       System.out.println(result1);

        Comparator<Integer> naturalOrder = (iBoxed, jBoxed) -> {
            //自动拆箱
            int i = iBoxed, j = jBoxed;
            return i < j ? -1 : (i == j ? 0 : 1);
        };
        int result2 = naturalOrder.compare(new Integer(42), new Integer(42));
        // 0
        System.out.println(result2);

        Long sum = 0L;
        for (long i = 0; i < Integer.MAX_VALUE; i++) {
            sum += i;
            System.out.println(sum);
        }

        Map<String, String> map = new HashMap<>();
        Map<String, String> map = new LinkedHashMap<>();

        Class<? extends Set<String>> cl = (Class<? extends Set<String>>) Class.forName("java.util.HashSet");
//        Class<? extends Set<String>> cl = (Class<? extends Set<String>>) Class.forName("java.util.TreeSet");
        Constructor<? extends Set<String>> cons = cl.getDeclaredConstructor();
        Set<String> s = cons.newInstance();
        s.addAll(Arrays.asList("a", "aa", "bbb", "qqq", "asd"));
        //使用TreeSet:[a, aa, asd, bbb, qqq]
        //使用HashSet:[aa, qqq, a, bbb, asd]
        System.out.println(s);