使用 Java 8 Lambda 表达式将 String 数组转换为 Map
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/31693781/
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
Convert String array to Map using Java 8 Lambda expressions
提问by bsam
Is there a better functional way of converting an array of Strings in the form of "key:value" to a Mapusing the Java 8 lambda syntax?
是否有更好的功能方法将“key:value”形式的字符串数组转换为Map使用 Java 8 lambda 语法的字符串？
Arrays.asList("a:1.0", "b:2.0", "c:3.0")
.stream()
.map(elem -> elem.split(":")
.collect(Collectors.toMap(keyMapper?, valueMapper?));
The solution I have right now does not seem really functional:
我现在的解决方案似乎并没有真正起作用：
Map<String, Double> kvs = new HashMap<>();
Arrays.asList("a:1.0", "b:2.0", "c:3.0")
.stream()
.map(elem -> elem.split(":"))
.forEach(elem -> kvs.put(elem[0], Double.parseDouble(elem[1])));
采纳答案by Eran
You can modify your solution to collect the Streamof Stringarrays into a Map(instead of using forEach) :
您可以修改您的解决方案以将StreamofString数组收集到 a Map（而不是使用forEach）中：
Map<String, Double> kvs =
Arrays.asList("a:1.0", "b:2.0", "c:3.0")
.stream()
.map(elem -> elem.split(":"))
.collect(Collectors.toMap(e -> e[0], e -> Double.parseDouble(e[1])));
Of course this solution has no protection against invalid input. Perhaps you should add a filter just in case the split String has no separator :
当然，这个解决方案没有针对无效输入的保护。也许您应该添加一个过滤器，以防拆分字符串没有分隔符：
Map<String, Double> kvs =
Arrays.asList("a:1.0", "b:2.0", "c:3.0")
.stream()
.map(elem -> elem.split(":"))
.filter(elem -> elem.length==2)
.collect(Collectors.toMap(e -> e[0], e -> Double.parseDouble(e[1])));
This still doesn't protect you against all invalid inputs (for example "c:3r"would cause NumberFormatExceptionto be thrown by parseDouble).
这仍然不能保护您免受所有无效输入的影响（例如"c:3r"会导致NumberFormatException被 抛出parseDouble）。
