J2ME中的Asin，Acos，Atan [英] Asin, Acos, Atan in J2ME

问题描述

如何在J2ME应用程序中使用Math.asin()(..等)?

How could I use Math.asin() (.. etc.) in a J2ME application?

(我看过 Real Java (看起来它可以做到)说我应该避免从字符串转换.如何从double值创建新的Real?)

(I've looked at Real Java (and it looks like it could do this) but it says I should avoid converting from a string. How could I create a new Real from a double value?)

推荐答案

从MIDP 2.0开始，此方法应该起作用:

Since MIDP 2.0 this should work:

public static double asin(double a)
{
    // -1 < a < 1
    // The function isn't very precise
    final double epsilon=1.0E-7; // Use this to adjust precision
    double x=a;
    // Newton's iterative method
    do x-=(Math.sin(x)-a)/Math.cos(x);
    while (Math.abs(Math.sin(x)-a)>epsilon);
    return x;
    // returned angle is in radians
}

但是，嘿， Real-Java 看起来非常不错.您绝对应该使用它.
如果仅使用一次或几次使用String分配数字，则不会影响应用程序的速度.

But hey, that Real - Java looks very nice. You definitely should use it.
If you assign the number using String only one or a few times, that won't affect your application's speed.

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