Convert String Array to Map Using Java 8 Lambda Expressions
Is There a Better Functional Way of Converting an Array of Strings in the Form of "Key: Value" to a Map Using the Java 8 Lambda Syntax? Arrays. asList("a:1.0"...
Is there a better functional way of converting an array of Strings in the form of "key:value" to a Map using the Java 8 lambda syntax?
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:
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])));
1 Answer
You can modify your solution to collect the Stream of String arrays into a Map (instead of using forEach) :
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 :
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 NumberFormatException to be thrown by parseDouble).
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