Stream with java

?Stream?was one of the major features added to Java 8.

A stream is a sequence of objects that supports various methods which can be pipelined to produce the desired result.

java stream provide many features to developer like:

• A stream is not a data structure instead it takes input from the Collections, Arrays or I/O channels.
• Streams don’t change the original data structure, they only provide the result as per the pipelined methods.
• Each intermediate operation is lazily executed and returns a stream as a result, hence various intermediate operations can be pipelined. Terminal operations mark the end of the stream and return the result.

how i can create stream in java project

for example i have the following code list of some thing object and i want put this list inside stream to print each object inside list

private static Employee[] arrayOfEmps = {
    new Employee(1, "Jeff Bezos", 100000.0), 
    new Employee(2, "Bill Gates", 200000.0), 
    new Employee(3, "Mark Zuckerberg", 300000.0)
};

private static List<Employee> empList = Arrays.asList(arrayOfEmps);

empList.stream().forEach(employee->{ // here i use lambda expression
  system.out.printLn(employee.toString());
  });
 
  
  

          

the above code i will run the code and print all arrayOfEmps by stream API

you can read about lambda expression when click here

now i want say about FUNCTIONAL INTERFACES USED IN JAVA STREAMS

Stream.java?provides different methods to process list elements,?map(),?flatMap(),?filter(),?sorted()?etc, each of which takes a functional interface type as an argument.

in the following code i will provide filtered Name array using lambda expression with stream API

String[] names=["shamk x1","cat x2","look","like"];

// now i will filter name and i need name 1

List<Employee> empList = Arrays.asList(arrayOfEmps);

List<String> filteredName=empList.stream()
      .fliter(name->name.contains("a"))
 // i will filter the name when match when return true
        ).collect(Collectors.toList); // return all match to list

        

now how the filter work inside stream API

the filter structures inside stream interface like following image

the filter take Predicate as an argument

so what is Predicate?

A predicate is a?functional interface?provided in?java.util.function?package and contains one abstract method, which is,?boolean test(T t).

you can see the following image to understand predicate

but now i think you don't understand how you can implement test inside functional interface

okay! look at the following code

.fliter(name->name.contains("x"))        

i used this code when write the filter name code and the lambda expression here is the implement of test method inside Predicate interface

you can see the following image to understand filter life cycle inside stream api

the next article i will explain about other method in stream API ....