Java：字符串与用于存储点的自定义类

Question

I am dealing with a large set of X,Y,Z points. What will be the best way to store all of the points if I need to keep RAM usage low? A string "X,Y,Z", a custom class, or would it not make any difference either way?

Answer 1

Strings are almost definitely a wrong choice: they waste about half the space, if not more, and they make you waste CPU cycles to get the data back into the numeric format suitable for processing.

A custom class with three primitive fields is a much better choice. Depending on the range and the type of your points, use byte , short , int , long , float , or double . This helps you avoid parsing the coordinates every time you are about to use your points.

Answer 2

为什么不包含3个元素的数组？

Answer 3

You can make one array to store X, Y, Z together, if you want to achieve low memory usage.

For a point with index i you can store X, Y, Z in array elements with following indexes:

• 0 + 3*i for X
• 1 + 3*i for Y
• 2 + 3*i for Z

Edit: This approach also has the following important advantages, which might in some circumstances be very handy:

• Puts all the data of the geometry algorithm in a contiguous place in memory, making CPU cache much more efficient.
• It's doesn't clutter memory management with a ton of small objects.

You can of course wrap this big table with a class with methods like getX(int index) to make it more readable for a little CPU cost.