JDK 8: Stream API

Stream API

• The Stream interface is located in the java.util.stream package.
• It represents a sequence of objects somewhat like the Iterator interface. However, unlike the Iterator, it supports parallel execution.
• The Stream interface supports the map/filter/reduce pattern and executes lazily, forming the basis (along with lambdas) for functional-style programming in Java 8.
• There are also corresponding primitive streams (IntStream, DoubleStream, and LongStream) for performance reasons.

How to create Stream which are multi core friendly

try (FileReader fr = new FileReader("text.txt");

BufferedReader br = new BufferedReader(fr)) {

// Read the line and Print

br.lines().forEach(System.out::println);

// Read the line and sort

br.lines().sorted(( x1, x2) -> x1.compareTo(x2))

.forEach(System.out::println);

// Read the line and sort and filter and finally print

br.lines().sorted((String x1, String x2) -> x1.compareTo(x2))

.filter(line -> line.contains("x"))

.forEach(System.out::println);

} catch (Exception e) {

// TODO: handle exception

e.printStackTrace();

}

Stream API operations

• There are several static methods on the  java.nio.file.Files class for navigating file trees using a Stream.
• list(Path dir) – Stream of files in the given directory.
• walk(Path dir)– Stream that traverses the file tree depth-first starting at the given directory.
• walk(Path dir, int maxDepth) – Same as walk(dir) but with a maximum depth.
• Streaming text pattern

Pattern patt = Pattern.compile(",");

patt.splitAsStream("a,b,c").forEach(System.out::println);