LinkedHashMap foreach循环中的递增计数器

Question

我正在遍历一个LinkedHashMap并递增I counter，下面是我使用for循环的方式

int i = 0;

for (Map.Entry<String, String> entry : linkedHashMap.entrySet()) {

      Car car = new Car();

      car.setCarId(String.valueOf(i++));
      car.setCarName(entry.getKey());
      car.setOdometerReading(entry.getValue());

      appRoomRepository.insertCarDetails(car);

}

int i = 0;

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {

     linkedHashMap.forEach((key, value) -> {

           Car car = new Car();

           car.setCarId(String.valueOf(i++));
           car.setCarName(key);
           car.setOdometerReading(value);

           appRoomRepository.insertCarDetails(car);

        });
}

Answer 1

Lambda表达式可以使用在外部作用域中定义的变量它们可以捕获静态变量、实例变量和局部变量，但只有局部变量必须是final或实际上是final

使用AtomicInteger：

AtomicInteger i = new AtomicInteger(0);

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {

     linkedHashMap.forEach((key, value) -> {

           Car car = new Car();

           car.setCarId(String.valueOf(i.getAndIncrement()));
           car.setCarName(entry.getKey());
           car.setOdometerReading(entry.getValue());

           appRoomRepository.insertCarDetails(car);

        });
}

```