下面将使用几个例子像你演示如何使用stream.sorted()
方法对List
进行排序。
1. 对字符串进行排序
1.1 配合Comparator.naturalOrder()
方法对List进行排序(在本例中就是按字母序,升序排列)。
package com.mkyong.sorted;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
public class StreamApplication {
public static void main(String[] args) {
List<String> list = Arrays.asList("9", "A", "Z", "1", "B", "Y", "4", "a", "c");
/*
List<String> sortedList = list.stream()
.sorted(Comparator.naturalOrder())
.collect(Collectors.toList());
List<String> sortedList = list.stream()
.sorted((o1,o2)-> o1.compareTo(o2))
.collect(Collectors.toList());
*/
// 使用String的默认比较方法,也就是按字母序进行排序
List<String> sortedList = list.stream().sorted().collect(Collectors.toList());
sortedList.forEach(System.out::println);
}
}
输出
1
4
9
A
B
Y
Z
a
c
1.2 配合Comparator.reverseOrder()
方法对List进行排序(即按字母序,降序排列)。
package com.mkyong.sorted;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;
public class StreamApplication {
public static void main(String[] args) {
List<String> list = Arrays.asList("9", "A", "Z", "1", "B", "Y", "4", "a", "c");
/*
List<String> sortedList = list.stream()
.sorted((o1,o2)-> o2.compareTo(o1))
.collect(Collectors.toList());
*/
List<String> sortedList = list.stream()
.sorted(Comparator.reverseOrder())
.collect(Collectors.toList());
sortedList.forEach(System.out::println);
}
}
输出
c
a
Z
Y
B
A
9
4
1
2. 对对象进行排序
2.1 按照年龄升序排列。
package com.mkyong.sorted;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;
public class StreamApplication {
static List<User> users = Arrays.asList(
new User("C", 30),
new User("D", 40),
new User("A", 10),
new User("B", 20),
new User("E", 50));
public static void main(String[] args) {
/*List<User> sortedList = users.stream()
.sorted((o1, o2) -> o1.getAge() - o2.getAge())
.collect(Collectors.toList());*/
List<User> sortedList = users.stream()
.sorted(Comparator.comparingInt(User::getAge))
.collect(Collectors.toList());
sortedList.forEach(System.out::println);
}
static class User {
private String name;
private int age;
public User(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "User{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
}
}
输出
User{name='A', age=10}
User{name='B', age=20}
User{name='C', age=30}
User{name='D', age=40}
User{name='E', age=50}
2.2 逆序排列
List<User> sortedList = users.stream()
.sorted(Comparator.comparingInt(User::getAge)
.reversed())
.collect(Collectors.toList());
sortedList.forEach(System.out::println);
输出
User{name='E', age=50}
User{name='D', age=40}
User{name='C', age=30}
User{name='B', age=20}
User{name='A', age=10}
2.3 根据名字升序排列
/*List<User> sortedList = users.stream()
.sorted((o1, o2) -> o1.getName().compareTo(o2.getName()))
.collect(Collectors.toList());*/
List<User> sortedList = users.stream()
.sorted(Comparator.comparing(User::getName))
.collect(Collectors.toList());