1. Introduction (look at the case first):

package com.stream;
/**
 * @author wxl
 */

/*
  Demand: Create and traverse the collection according to the requirements below
     Create a collection, store multiple string elements
   "Zhang Sanfeng", "Zhang Wuji", "Zhang Cuishan", "Wang Ermazi", "Zhang Liang", "Xie Guangkun"
     Store all the elements in the set "Zhang" to a new collection
     Store the elements of the length of the "Zhang" set at the beginning of the "Zhang" to a new collection
     The collection obtained in the previous step
*/
import java.util.Collections;
import java.util.stream.Collectors;
import java.util.List;
import java.util.ArrayList;
public class MyStream1 {
    public static void main(String []args) {
        // collection batch add elements
        ArrayList<String> list = new ArrayList();
        Collections.addAll(list, "Zhang Sanfeng","Zhang Wuji","Zhang Cuishan","Wang Ermazi","Zhang Liang","Xie Guangkun");

        // Traversing the list and adding the elements to the beginning to List1.
        ArrayList<String> list1 = new ArrayList<>();
        for (String s : list) {
            if(s.startsWith("open")) {
                list1.add(s);
            }
        }

        // Traversing the list1 collection, adding elements with a length of 3 to List2.
        ArrayList<String> list2 = new ArrayList<>();
        for (String s : list1) {
            if (s.length() == 3) {
                list2.add(s);
            }
        }

        for (String s : list2) {
            System.out.println(s);
        }


        // Apocastle: It is very convenient to handle with flowing
        List<String> list3 = list.stream().filter(s->s.startsWith("open")).collect(Collectors.toList());
        System.out.println(list3);
        List<String> list4 = list.stream().filter(s->s.startsWith("open")).filter(s->s.length()==3).collect(Collectors.toList());
        System.out.println(list4);
    }
}

result:

Task :MyStream1.main()
Zhang Sanfeng
Zhang Wuji
Zhang Cuishan
[Zhang Sanfeng, Zhang Wuji, Zhang Cuishan, Zhang Liang]
[Zhang Sanfeng, Zhang Wuji, Zhang Cuishan]

2. Explanation:

It seems that the operation is convenient and concise. In fact, the collection uses iterative and accumulators to achieve it, and the stream is declared to handle the data set (expressed by querying statements instead of temporarily writing one implementation). In addition,, in addition,, in addition,, in addition, Streaming can be processed in parallel without writing any multi -threaded code! If you have a impression first, you can use it.

3. Stream flow operation process (three types):

• Get the stream stream method
  Create an assembly line and put the data on the assembly line to prepare for operation. It is like a collection method that can directly call the stream (). This is the method of obtaining the stream.
• Intermediate method
  The operation on the assembly line is like Filter filtering, and the elements needed through conditions. This is the intermediate method
• Ending method
  A Stream stream can only have one ending method, the last operation on the streamline. When using the flow, this process is all operational flow. In the end, you have to turn the flow into a collection or print it or calculate. These methods are the ending method of the stream, such as Collection (Collectors.tolist ()).

4. Summary: Section 02 Introduction to stream stream acquisition method