java-stream Getting started with java-stream
Remarks
This section provides an overview of what java-stream is, and why a developer might want to use it.
It should also mention any large subjects within java-stream, and link out to the related topics. Since the Documentation for java-stream is new, you may need to create initial versions of those related topics.
Installation or Setup
Detailed instructions on getting java-stream set up or installed.
Working with Java Stream Api (Java 8) in Android using Android Studio
Gradle Setup :
build.gradle(Module: app)
compileOptions { sourceCompatibility JavaVersion.VERSION_1_8 targetCompatibility JavaVersion.VERSION_1_8 } jackOptions { enabled true } What is the Stream API ?
Stream is a new abstract layer introduced in Java 8. A stream is a sequence of elements (objects, primitive types) from the stream source. Therefore, stream is not a data structure and it doesn’t store the elements it works with. It can be of a finite or infinite size and allow effortless code parallelism
Advantage's:
- It helps in using data in a declarative way. We can make use of Database functions like Max, Min etc., without running a full iteration.
- It makes good use of multi-core architectures without worrying about multi-threading code.
- We can create a pipeline of data operations with Java Stream that can run in a sequence or in parallel.
- It provides support for group by, order by etc. operations.
- It supports writing for code in Functional programming style.
- It provides parallel processing of data.
How streams work :
Normal Approach (Without using Stream Api) :
List<Integer> numbers = new ArrayList<>(); numbers.addAll(Arrays.asList(1, 20, 3, 10, 20, 30, 4, 50, 80, 1, 2));//adding dummy data int i = 0; List<String> number_str = new ArrayList<>(); for (Integer num : numbers) { if (i >= 5)//after 5 loop will stop break; if (num >= 10) // check number greater than or equal to 10 { number_str.add(String.format("Number %d", num));//Typecast Integer to String then add to String List i++;//increment i count } } number_str.sort(Comparator.naturalOrder());//sort the list In Above code we created Integer List and add some data's then Iterate using for loop. On each loop execution we check loop count(i >= 5 ) and num >=10 . finally sort the string list.
Now, let’s rewrite the code using Java’s 8 Stream API:
List<Integer> numbers = new ArrayList<>(); numbers.addAll(Arrays.asList(1, 20, 3, 10, 20, 30, 4, 50, 80, 1, 2)); List<String> number_str = numbers.stream() .filter(num -> num >= 10)//check num greater than 10 .limit(5)//stop loop at 5 .sorted()//sort the list .map(num -> String.format("Number %d", num))//typecast into String List .collect(Collectors.toList()); 
