Magic Number - Intro to Java Programming Udacity English Vietnamese

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Education 4.8K views 20 likes 3 dislikes 23 Feb 2015

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Now, there's just one little blemish to the program that we've just written. It

Có một thiếu sót nhỏ với chương trình ta vừa viết.

uses what programmers refer to as magic numbers. Look at this line over here,

Nó có một cái mà programmers thường gọi là "magic number". Hãy nhìn cái dòng này,

and it begs to question why 25, why 255? Those look like values that a magician

25 là cái gì, sao lại là 255? Có phải mấy cái số này là những thứ

picked out of a hat. Instead of using magic numbers, it's a good idea to use

mà ảo thuật gia lấy ra từ cái mũ? Thay vì sử dụng các số "magic number" này, ý tưởng tốt hơn

constants. Here is how you do this in Java. The keyword, final, indicates a

là sử dụng constants (hằng số). Đây là cách bạn làm trong Java. Từ khóa là <i>final</i>,

number that can never be changed that has assumed it's final value. Or like we

ám chỉ một số mà không thể thay đổi vì nó đã là giá trị "cuối cùng" (final).

would say in math, it's a constant value. So here, are the 25, I'll call it

Hay giống như ta nói trong môn toán, nó là hằng số. Nên ở đây, số 25, tôi gọi nó

added red and the 255 here, called max red. I defined these as variables just

là ADDED-RED và 255 ở đây gọi là MAX_RED. Tôi đã định nghĩa chúng

like you would define any other variable, except for the keyword final in

cũng giống như khi định nghĩa các biến khác, ngoại trừ từ khóa <i>final</i> ở trước.

front. And also, it's a convention amongst Java programmers, that constants

Và đó cũng là quy ước với toàn bộ programmers, là hằng số

should be written in upper case. Maybe with an occasional underscore. Now, go

nên được viết HOA hết. Có thể dùng cùng với các dấu gạch dưới.

ahead and rewrite the statement here, using these two constants instead of the

Giờ, tiếp tục và viết lại câu lệnh ở đây, sử dụng 2 hằng số này

magic numbers. And put your answers into this box.

thay vì cái "magic number" kia. Và cho câu trả lời của bạn vào trong ô này.

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