java Java中的基数方向算法
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/2131195/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Cardinal direction algorithm in Java
提问by MattyW
This weekend I spend a few minutes thrashing together an algorithm that would take in a heading (in degrees) and return a String for the cardinal direction (I'm using it in an android compass application I'm using). What I ended up with was this:
这个周末我花了几分钟时间研究一个算法，该算法将接收一个航向（以度为单位）并返回一个字符串作为主要方向（我在我正在使用的 android 指南针应用程序中使用它）。我最终得到的是这样的：
private String headingToString(Float heading)
{
String strHeading = "?";
Hashtable<String, Float> cardinal = new Hashtable<String, Float>();
cardinal.put("North_1", new Float(0));
cardinal.put("Northeast", new Float(45));
cardinal.put("East", new Float(90));
cardinal.put("Southeast", new Float(135));
cardinal.put("South", new Float(180));
cardinal.put("Southwest", new Float(225));
cardinal.put("West", new Float(270));
cardinal.put("Northwest", new Float(315));
cardinal.put("North_2", new Float(360));
for (String key: cardinal.keySet())
{
Float value = cardinal.get(key);
if (Math.abs(heading - value) < 30)
{
strHeading = key;
if (key.contains("North_"))
{
strHeading = "North";
}
break;
}
}
return strHeading;
}
My question is, is this the best way of doing this? It must have been done many times before although I haven't done a search for examples on the web yet. Have any other people tried this and found a neater solution?
我的问题是，这是最好的方法吗？虽然我还没有在网上搜索过例子，但之前肯定已经做过很多次了。有没有其他人尝试过这个并找到了更简洁的解决方案？
Edit for The Reverand's Thilo's, shinjin's and Chrstoffer's responses:
编辑 The Reverand 的 Thilo、shinjin 和 Chrstoffer 的回应：
The Solution
解决方案
public static String headingToString2(double x)
{
String directions[] = {"N", "NE", "E", "SE", "S", "SW", "W", "NW", "N"};
return directions[ (int)Math.round(( ((double)x % 360) / 45)) ];
}
回答by Reverend Gonzo
That's fine in most cases, though to make it optimized and (IMO) cleaner, what you could do is find a function to relate the input heading to one used in the map.
在大多数情况下这很好，但为了使其优化和（IMO）更清晰，您可以做的是找到一个函数将输入标题与地图中使用的标题相关联。
For example: (I'm pretty sure this is right, but you'll want to check it)
例如：（我很确定这是正确的，但您需要检查一下）
45* (int)Math.round(( ((double)x % 360) / 45))
What this does is first x % 360makes sure the heading is within a valid range. then
这首先x % 360确保标题在有效范围内。然后
45 * round(.../45)
finds the closest multiple of 45.
找到最接近的 45 倍数。
Now change your map to be
现在将您的地图更改为
HashMap<Integer, String> map = new HashMap<Integer, String>()
map.put(0, "North")
map.put(45, "Northeast")
etc...
So, now your algorithm becomes a fast mathemtical calculation rather than iterating through the map. Furthermore, you don't need as Hashtable here since it provides constructs for concurrency (if I remember correctly) and in your case it would actually cause a performance decrease.
所以，现在你的算法变成了快速的数学计算，而不是遍历地图。此外，您在这里不需要 as Hashtable，因为它提供了并发构造（如果我没记错的话），在您的情况下，它实际上会导致性能下降。
Once again, the performance hit may be completely negligible for your needs.
再一次，性能影响对于您的需求可能完全可以忽略不计。
Edit for Thilo's and shinjin's suggestions:
针对 Thilo 和 Shinjin 的建议进行编辑：
Instead of multiplying by 45, just keep the rest of the equation, which gives you values for 0-7, and make an array of your strings.
而不是乘以 45，只需保留等式的其余部分，即为您提供 0-7 的值，并制作一个字符串数组。
String directions[] = {"N", "NE", "E", "SE", "S", "SW", "W", "NW"}
return directions[ (int)Math.round(( ((double)x % 360) / 45)) % 8 ]
and you've got your problem solved in two lines.
你的问题用两行解决了。
One note: Modulus won't work correctly for negative numbers. If our input heading is negative, you'll need to make it positive first.
一个注意事项：模数对于负数将无法正常工作。如果我们的输入标题为负，您需要先将其设为正。
回答by magdalar
Most of the answers here are off by 22.5 degrees for their 45 degree intervals, and map e.g. 0-45 as N, rather than [337.5-360],[0-22.5] to N. You need to offset before doing the math to correct for this.
这里的大多数答案在 45 度间隔内偏离 22.5 度，并将例如 0-45 映射为 N，而不是 [337.5-360],[0-22.5] 到 N。您需要在进行数学运算之前进行偏移对此是正确的。
Here's a solution that uses 22.5 degree intervals, such as you might see for wind directions:
这是一个使用 22.5 度间隔的解决方案，例如您可能会看到风向：
private String formatBearing(double bearing) {
if (bearing < 0 && bearing > -180) {
// Normalize to [0,360]
bearing = 360.0 + bearing;
}
if (bearing > 360 || bearing < -180) {
return "Unknown";
}
String directions[] = {
"N", "NNE", "NE", "ENE", "E", "ESE", "SE", "SSE",
"S", "SSW", "SW", "WSW", "W", "WNW", "NW", "NNW",
"N"};
String cardinal = directions[(int) Math.floor(((bearing + 11.25) % 360) / 22.5)];
return cardinal + " (" + formatBearing.format(bearing) + " deg)";
}
回答by Andrei
The previous examples are not accurate, here is a more accurate solution in JavaScript.
前面的例子不准确，这里是 JavaScript 中更准确的解决方案。
function getCardinalDirection(input) {
var directions = ["N", "NE", "E", "SE", "S", "SW", "W", "NW", "N"];
var index = Math.floor( ((input-22.5)%360) / 45 );
return directions[index+1];
}
回答by Thilo
You could maybe add 15 degrees up front to avoid North_1 and North_2.
您可以在前面增加 15 度以避免 North_1 和 North_2。
回答by outaTiME
in java:
在Java中：
String _directions[] = {"N", "NE", "E", "SE", "S", "SW", "W", "NW"};
public String getHeading(int hea) {
return _directions[(int)Math.floor((hea % 360) / 45)];
}
In "java" case u must need to create a Class.
在“java”的情况下，你必须需要创建一个类。
in javascript:
在 JavaScript 中：
var _directions = ["N", "NE", "E", "SE", "S", "SW", "W", "NW"];
function getDirection (hea) {
return _directions[Math.floor((hea % 360) / 45)];
};
