Java8排序stream.sorted()的使用

更新時間：2021年03月17日 09:55:22 作者：延陵縹緲

這篇文章主要介紹了Java8排序stream.sorted()的使用，文中通過示例代碼介紹的非常詳細(xì)，對大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價值，需要的朋友們下面隨著小編來一起學(xué)習(xí)學(xué)習(xí)吧

在這個頁面上我們將提供java 8 Stream sorted（）示例。我們可以按照自然排序以及Comparator提供的排序?qū)α鬟M(jìn)行排序。在java 8中Comparator可以使用lambda表達(dá)式進(jìn)行實(shí)例化。我們還可以反轉(zhuǎn)自然排序以及提供的排序Comparator。自然排序使用提供的順序Comparable，必須由其實(shí)例是流元素的類實(shí)現(xiàn)。在這個頁面上我們將排序List，Map并Set使用java 8流sorted()方法。

1.sorted()方法的語法示例。

1.1sorted()：它使用自然順序?qū)α鞯脑剡M(jìn)行排序。元素類必須實(shí)現(xiàn)Comparable接口。

按自然升序?qū)线M(jìn)行排序

list.stream().sorted() .stream().sorted();

自然序降序使用Comparator提供reverseOrder()方法

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

1.2 sorted(Comparator<? super T> comparator):這里我們創(chuàng)建一個Comparator使用lambda表達(dá)式的實(shí)例。我們可以按升序和降序?qū)α髟剡M(jìn)行排序。

使用Comparator來對列表進(jìn)行自定義升序。

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

使用Comparator提供reversed()方法來對列表進(jìn)行自定義降序。。

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

2.使用List流排序（）

package com.stream.demo;
 
import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;
 
public class StreamListDemo {
 public static void main(String[] args) {
 List<Student> 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<Student> 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()));
 }
}

package com.stream.demo;
 
public class Student implements Comparable<Student> {
 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;
 }
}

執(zhí)行結(jié)果

---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

3.使用set流排序

package com.stream.demo;
 
import java.util.Comparator;
import java.util.HashSet;
import java.util.Set;
 
public class StreamSetDemo {
 public static void main(String[] args) {
 Set<Student> set = new HashSet<>();
 set.add(new Student(1, "Mahesh", 12));
 set.add(new Student(2, "Suresh", 15));
 set.add(new Student(3, "Nilesh", 10));
 
 System.out.println("---Natural Sorting by Name---");
 System.out.println("---Natural Sorting by Name---");
 set.stream().sorted().forEach(e -> System.out.println("Id:"
   + e.getId() + ", Name: " + e.getName() + ", Age:" + e.getAge()));
 
 System.out.println("---Natural Sorting by Name in reverse order---");
 set.stream().sorted(Comparator.reverseOrder()).forEach(e -> System.out.println("Id:"
   + e.getId() + ", Name: " + e.getName() + ", Age:" + e.getAge()));
 
 System.out.println("---Sorting using Comparator by Age---");
 set.stream().sorted(Comparator.comparing(Student::getAge))
   .forEach(e -> System.out.println("Id:" + e.getId() + ", Name: " + e.getName() + ", Age:" + e.getAge()));
 
 System.out.println("---Sorting using Comparator by Age in reverse order---");
 set.stream().sorted(Comparator.comparing(Student::getAge).reversed())
   .forEach(e -> System.out.println("Id:" + e.getId() + ", Name: " + e.getName() + ", Age:" + e.getAge()));
 }
}

4.使用Map流排序

package com.stream.demo;
 
import java.util.Comparator;
import java.util.HashMap;
import java.util.Map;
 
public class StreamMapDemo {
 public static void main(String[] args) {
 Map<Integer, String> map = new HashMap<>();
 map.put(15, "Mahesh");
 map.put(10, "Suresh");
 map.put(30, "Nilesh");
 
 System.out.println("---Sort by Map Value---");
 map.entrySet().stream().sorted(Comparator.comparing(Map.Entry::getValue))
   .forEach(e -> System.out.println("Key: "+ e.getKey() +", Value: "+ e.getValue()));
 
 System.out.println("---Sort by Map Key---");System.out.println("---Sort by Map Key---");
 map.entrySet().stream().sorted(Comparator.comparing(Map.Entry::getKey))
   .forEach(e -> System.out.println("Key: "+ e.getKey() +", Value: "+ e.getValue()));
 }
}

這是在英文網(wǎng)站看到的示例，覺得還不錯就翻譯過來了。

原文鏈接：http://www.concretepage.com/java/jdk-8/java-8-stream-sorted-example

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