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Java8排序stream.sorted()的使用

    在这个页面上我们将提供java 8 Stream sorted（）示例。我们可以按照自然 排序 以及Comparator提供的排序对流进行排序。在java 8中Comparator可以使用lambda表达式进行实例化。我们还可以反转自然排序以及提供的排序Comparator。自然排序使用提供的顺序Comparable，必须由其实例是流元素的类实现。在这个页面上我们将排序List，Map并Set使用java 8流sorted()方法。

1.sorted()方法的语法示例。 

1.1sorted()：它使用自然顺序对流的元素进行排序。元素类必须实现Comparable接口。 

按自然升序对集合进行排序

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

自然序降序使用Comparator提供reverseOrder()方法

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

1.2 sorted(Comparator<? super T> comparator):这里我们创建一个Comparator使用lambda表达式的实例。我们可以按升序和降序对流元素进行排序。 

使用Comparator来对列表进行自定义升序。 

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list.stream().sorted(Comparator测试数据paring(Student::getAge)) .stream().sorted(Comparator测试数据paring(Student::getAge));

使用Comparator提供reversed()方法来对列表进行自定义降序。 。 

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list.stream().sorted(Comparator测试数据paring(Student::getAge).reversed()) .stream().sorted(Comparator测试数据paring(Student::getAge).reversed());

2.使用List流排序（）

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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测试数据paring(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测试数据paring(Student::getAge).reversed()).collect(Collectors.toList());

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

  }

}

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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测试数据pareTo(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;

  }

}

执行结果

---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

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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测试数据paring(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测试数据paring(Student::getAge).reversed())

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

  }

}

4.使用Map流排序

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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测试数据paring(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测试数据paring(Map.Entry::getKey))

    .forEach(e -> System.out.println( "Key: " + e.getKey() + ", Value: " + e.getValue()));

  }

}

这是在英文网站看到的示例，觉得还不错就翻译过来了。

原文链接： http://HdhCmsTestconcretepage测试数据/java/jdk-8/java-8-stream-sorted-example

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原文链接：https://blog.csdn.net/qq_34996727/article/details/94472999

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