Java double 不会否定!为什么？

Question

出于某种原因，我无法否定 double ，然后在满足特定条件(正在)时返回它。尽管有任何其他哄骗，它仍然是积极的。

 public static double angleDiffNoAbs(double from, double to, double maxValue) {  
  double diff = to - from;
  double absdiff = Math.abs(diff);

  if (absdiff > maxValue) {
   double newdiff;

   boolean clockwise = false;

   if (from < to) {
    newdiff = maxValue;
    clockwise = true;
    System.out.println("c");
   } else {
    System.out.println("ac");
    newdiff = maxValue * -1.0d;
   }

   System.out.println("from: " + from + ", to: " + to + ", diff: " + diff + ", absdiff: " + absdiff + ", newdiff(limited): " + newdiff + ", wound: " + (clockwise ? "clockwise" : "anti-clockwise"));

   return newdiff;
  }

  double result = ((180d + diff) % 360d) - 180d;
  if (result < -180d) result = 360d + result;

  return result;
 }

我的 JUnit 测试结果是:

c
from: -10.0, to: 20.0, diff: 30.0, absdiff: 30.0, newdiff(limited): 10.0, wound: clockwise
ac
from: 20.0, to: -10.0, diff: -30.0, absdiff: 30.0, newdiff(limited): 10.0, wound: anti-clockwise

我一直在研究这个问题，但无法找出问题所在。 JUnit 测试如下(如果有帮助):

public class AngleDiffTest {
 @Test
 public void testAngleDiff() {
  double diff = Math.abs(Player.angleDiffNoAbs(353, 12, 360f));
  Assert.assertFalse("diff > 200: " + diff, diff > 200);
 }

 @Test
 public void testAngleDiff2() {
  double diff2 = Math.abs(Player.angleDiffNoAbs(360, 0, 360f));
  Assert.assertFalse("diff2 > 200: " + diff2, diff2 > 200);
 }

 @Test
 public void testAngleDiff3() {
  double diff2 = Math.abs(Player.angleDiffNoAbs(-10d, 20d, 10d));
  Assert.assertEquals("diff2 != 10.0: " + diff2, 10d, diff2);
 }


 @Test
 public void testAngleDiff4() {
  double diff2 = Math.abs(Player.angleDiffNoAbs(20d, -10d, -10d));
  Assert.assertEquals("diff2 != -10.0: " + diff2, -10d, diff2);
 } 
}

Answer 1

from: 20.0, to: -10.0, diff: -30.0, absdiff: 30.0, newdiff(limited): 10.0, wound: anti-clockwise

此结果似乎来自您的第四个测试用例 ( testAngleDiff4 )，您在其中传递了 -10d 的负值对于 maxValue .当你做 newdiff = maxValue * -1.0d ，两个否定相抵消，留下一个肯定的答案。