A simple example of the lambda expression and stream class in Java

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How does a Java lambda expression and stream work???

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The syntax of a lambda expression

Basic syntax:

(parameters) -> expression或(parameters) ->{ statements; }

Read the example study!

Example one: Define a Ayperson class to prepare for subsequent tests.

package com.evada.de;import java.util.Arrays;import java.util.List;class AyPerson{    private String id;    private String name;    public String getId() {        return id;    }    public void setId(String id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public AyPerson(String id, String name) {        this.id = id;        this.name = name;    }}/** * Created by Ay on 2016/5/9. */public class LambdaTest {    public static void main(String[] args) {        List<String> names = Arrays.asList("Ay", "Al", "Xy", "Xl");        names.forEach((name) -> System.out.println(name + ";"));    }}

The above example Names.foreach (name), SYSTEM.OUT.PRINTLN (name + ";"));
Similar to:

function (name) {//name is a parameter
SYSTEM.OUT.PRINTLN (name + ";"); /Method Body
}

Results:

Ay;Al;Xy;Xl;

Example two: Copy the following code into the main function above

List<Student> personList = new ArrayList<>();personList.add(new Student("00001","Ay"));personList.add(new Student("00002","Al"));personList.add(new Student("00003","To"));personList.forEach((person) -> System.out.println(person.getId()+ ":" + person.getName()));

Results:

00001:Ay00002:Al00003:To

Example three: F**ilter () * * method in Lambda and stream classes

List<AyPerson> personList = new ArrayList<>();    personList.add(new AyPerson("00001","Ay"));    personList.add(new AyPerson("00002","Al"));    personList.add(new AyPerson("00003", "To"));    //stream类中的filter方法    personList.stream()            //过滤集合中person的id为00001            .filter((person) -> person.getId().equals("00001"))            //将过滤后的结果循环打印出来            .forEach((person) -> System.out.println(person.getId() + ":" + person.getName()));

Results:

00001:Ay

Example four: the collect () method in the Stream class,

    List<AyPerson> personList = new ArrayList<>();    List<AyPerson> newPersonList = null;    personList.add(new AyPerson("00001","Ay"));    personList.add(new AyPerson("00002","Al"));    personList.add(new AyPerson("00003", "To"));    //将过滤后的结果返回到一个新的List中    newPersonList = personList.stream()            .filter((person) -> person.getId().equals("00002")).collect(Collectors.toList());    //打印结果集    newPersonList.forEach((person) -> System.out.println(person.getId() + ":" + person.getName()));

In addition to the list can be placed in the set and so on ...

Results:

00002:Al

There are many useful ways to use the stream, such as count,limit and so on, you can learn from the API.

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A simple example of the lambda expression and stream class in Java