Let's begin by defining the term stream as it applies to the stream API:
A stream operates on a data source, such as an array or a collection. A stream, itself, never provides storage on a data. It simply moves data, possibly filtering, sorting, or otherwise operating on that data is the process. as a genral rule, however a stream operation by itself does not modyfy the data source. For Example: sorting a stream does not change the order of the source. Rather, sorting a stream results in the creation of a new stream that produces the sroted result.
A Simple Stream Example : Let's work through an example that uses streams. The following program creates an ArrayList called myList that holds a collection of integers. Next, it obtains a stream that uses myList as a source.

package streamclasses; import java.util.ArrayList; import java.util.Optional; import java.util.stream.Stream; /** * * @author manoj.vishwakarma */ public class StreamClassDemo { public static void main(String[] args) { //Create a list of integer Values ArrayList<Integer> myList=new ArrayList<Integer>(); myList.add(7); myList.add(18); myList.add(10); myList.add(5); myList.add(24); myList.add(17); myList.add(5); System.out.println("Original Lise:" +myList); //Obtain a stream to the array list. Stream<Integer> myStream=myList.stream(); //Obtain the minimum and maximum value by using of min(), max(), isPresent(), and get() Optional<Integer> minValu=myStream.min(Integer::compare); if(minValu.isPresent()){ System.out.println("Minimum Value:"+minValu.get()); } // Must obtain a new stream because previous call to min() is a terminal opration that consumed the stream //Max value myStream=myList.stream(); Optional<Integer> maxValu=myStream.max(Integer::compare); if(maxValu.isPresent()){ System.out.println("Max Value:"+maxValu.get()); } //Sort the stream by use of sorted() Stream<Integer> sortStream=myList.stream().sorted(); //Display the sorted stream by use of forEacg(). System.out.println("Sorted stream"); sortStream.forEach((n)->System.out.println(n+"")); //Dispaly only the odd values by use of filter() Stream<Integer> oddValue=myList.stream().sorted().filter((n)->(n%2)==1); //Display the sorted stream by use of forEacg(). System.out.println("Odd Values"); oddValue.forEach((n)->System.out.println(n+"")); //Display only the odd value that are greater than 5. Notice That two filter operations are pipelined oddValue=myList.stream().sorted().filter((n)->(n%2)==1) .filter((n)->n>5); System.out.println("Odd Values grater than 5:"); oddValue.forEach((n)->System.out.println(n+"")); } }
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