java8的sorted,Java8排序stream.sorted()

使用Java8排序stream.sorted()

sorted-example

国外对Java8一系列总结的不错， 翻译过来给你们共享

这篇文章将会讲解Java 8 Stream sorted()示例， 咱们可以以天然序或着用Comparator 接口定义的排序规则来排序一个流。Comparator 能用用lambada表达式来初始化， 咱们还可以逆序一个已经排序的流。

接下来咱们将会使用java 8 的流式sorted排序List 、Map 、 Set

一、sorted() 默认使用天然序排序， 其中的元素必须实现Comparable 接口

二、sorted(Comparator super T> comparator) ：咱们能够使用lambada 来建立一个Comparator 实例。能够按照升序或着降序来排序元素。

下面代码以天然序排序一个listweb

list.stream().sorted()

1

天然序逆序元素，使用Comparator 提供的reverseOrder() 方法ide

list.stream().sorted(Comparator.reverseOrder())

1

使用Comparator 来排序一个listsvg

list.stream().sorted(Comparator.comparing(Student::getAge))

1

把上面的元素逆序this

list.stream().sorted(Comparator.comparing(Student::getAge).reversed())

1

Stream sorted() with List

咱们排序一组装着Student 类对象的List 集合。 首先咱们使用天然序， 接着咱们使用Comparator 分别进行升序和降序：翻译

SortList.java

package com.concretepage;

import java.util.ArrayList;

import java.util.Comparator;

import java.util.List;

import java.util.stream.Collectors;

public class SortList {

public static void main(String[] args) {

List list = new ArrayList();

list.add(new Student(1, "Mahesh", 12));

list.add(new Student(2, "Suresh", 15));

list.add(new Student(3, "Nilesh", 10));

System.out.println("---Natural Sorting by Name---");

List slist = list.stream().sorted().collect(Collectors.toList());

slist.forEach(e -> System.out.println("Id:"+ e.getId()+", Name: "+e.getName()+", Age:"+e.getAge()));

System.out.println("---Natural Sorting by Name in reverse order---");

slist = list.stream().sorted(Comparator.reverseOrder()).collect(Collectors.toList());

slist.forEach(e -> System.out.println("Id:"+ e.getId()+", Name: "+e.getName()+", Age:"+e.getAge()));

System.out.println("---Sorting using Comparator by Age---");

slist = list.stream().sorted(Comparator.comparing(Student::getAge)).collect(Collectors.toList());

slist.forEach(e -> System.out.println("Id:"+ e.getId()+", Name: "+e.getName()+", Age:"+e.getAge()));

System.out.println("---Sorting using Comparator by Age with reverse order---");

slist = list.stream().sorted(Comparator.comparing(Student::getAge).reversed()).collect(Collectors.toList());

slist.forEach(e -> System.out.println("Id:"+ e.getId()+", Name: "+e.getName()+", Age:"+e.getAge()));

}

}

Student.java *code package com.concretepage;

public class Student implements Comparable {

private int id;

private String name;

private int age;

public Student(int id, String name, int age) {

this.id = id;

this.name = name;

this.age = age;

}

public int getId() {

return id;

}

public String getName() {

return name;

}

public int getAge() {

return age;

}

@Override

public int compareTo(Student ob) {

return name.compareTo(ob.getName());

}

@Override

public boolean equals(final Object obj) {

if (obj == null) {

return false;

}

final Student std = (Student) obj;

if (this == std) {

return true;

} else {

return (this.name.equals(std.name) && (this.age == std.age));

}

}

@Override

public int hashCode() {

int hashno = 7;

hashno = 13 * hashno + (name == null ? 0 : name.hashCode());

return hashno;

}

}

Output *xml

—Natural Sorting by Name—

Id:1, Name: Mahesh, Age:12

Id:3, Name: Nilesh, Age:10

Id:2, Name: Suresh, Age:15

—Natural Sorting by Name in reverse order—

Id:2, Name: Suresh, Age:15

Id:3, Name: Nilesh, Age:10

Id:1, Name: Mahesh, Age:12

—Sorting using Comparator by Age—

Id:3, Name: Nilesh, Age:10

Id:1, Name: Mahesh, Age:12

Id:2, Name: Suresh, Age:15

—Sorting using Comparator by Age with reverse order—

Id:2, Name: Suresh, Age:15

Id:1, Name: Mahesh, Age:12

Id:3, Name: Nilesh, Age:10对象