J2ME Game Development Notes integrated version

-------------General class Problems--------------

1 j2me table method using trigonometric functions

CLDC and MIDP do not provide trigonometric functions, and there is no floating-point number in the CLDC1.0, so our choice is to check the table. Use the sin and Cos tables with 8-bit fixed-point numbers. The following is the code in the WTK demo, which provides only a limited number of angles, which are used to refine the angle value as needed.

//Sines of angles 0, a, m, 90,all *256

private static final int[] Sines =< br>
{0, N, 128, 165, 196, 222, 241, 252, 256};

//angle is in DEGREES/10, i.e. 0..36 for full circle

private static int sineTimes256 (int angle)
　　br> {

angle%= 36; 360 degrees

if (angle <= 9)//0..90 degrees

{

return sines[angle];

}

Else if (angle <=)//90..180 degrees

{

return sines[18-angle];
br>}

Else if (angle <=)//180..270 degrees

{

return-sines[angle-18];

}

Else//270..360 degrees

{

Return-sines[36-angle];

}

}

//angle is in DEGREES/10, i.e. 0..36 to Full circle

private static int C osineTimes256 (int angle)

{

return sineTimes256(angle + 9); i.e. add degrees

}

(2006.5 Note: Some algorithms can generate trigonometric values so that you can save some data by generating a function table when the game is loaded)

2 J2ME Generates random numbers between 0~n with a random number of

:

(Ran.nextint () >>>1)%n

or

(Ran.nextint () &0x7f FFFFFF)%n

produces random numbers between-n~0:

(Ran.nextint () | 0x80000000)%n