Simple example of Lambda expression and Stream class in Java-javaTutorial-php.cn

Simple example of Lambda expression and Stream class in Java

黄舟

Release： 2017-01-17 15:14:07

Original

1408 people have browsed it

Ask a question

How to use Java's lambda expressions and Stream? ? ?

Solve the problem

The syntax of Lambda expression

Basic syntax:

[code](parameters) -> expression
或
(parameters) ->{ statements; }

Copy after login

Look at the examples to learn!

Example 1: Define an AyPerson class to prepare for subsequent testing.

[code]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 + ";"));
    }
}

Copy after login

The above example names.forEach((name) -> System.out.println(name + “;”));

is similar to:

function(name){//name为参数 
 
System.out.println(name + “;”);//方法体 
 
}

Copy after login

Result:

[code]Ay;
Al;
Xy;
Xl;

Copy after login

Example 2: Copy the following code into the main function above

[code]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()));

Copy after login

Result:

[code]00001:Ay
00002:Al
00003:To

Copy after login

Example 3: f**ilter( in Lambda and Stream classes )**Method

[code]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()));

Copy after login

Result:

1	`[code]00001:Ay`

Copy after login

Example 4: collect() method in Stream class,

[code]    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()));

Copy after login

##In addition to Put it in List, you can also put it in Set, etc...
Result:

1	`[code]00002:Al`

Copy after login

There are many useful methods that can be used in Stream, such as count, limit, etc. Go to the API to learn by yourself

The above is the content of simple examples of Lambda expressions and Stream classes in Java. For more related content, please pay attention to the PHP Chinese website ( www.php.cn)!