Java 中的 Collections.sort()，示例
原文:https://www . geesforgeks . org/collections-sort-Java-examples/
java.util.Collections . sort()方法存在于 Java . util . collections 类中。用于对集合中指定的列表中的元素进行升序排序。 它的工作原理类似于 java.util.Arrays.sort() 方法，但是它更好，因为它可以对 Array 的元素以及链表、队列和其中的更多元素进行排序。
public static void sort(List myList)
myList : A List type object we want to sort.
This method doesn't return anything
示例:
Let us suppose that our list contains
{"Geeks For Geeks", "Friends", "Dear", "Is", "Superb"}
After using Collection.sort(), we obtain a sorted list as
{"Dear", "Friends", "Geeks For Geeks", "Is", "Superb"}
按升序对数组列表进行排序
// Java program to demonstrate working of Collections.sort()
import java.util.*;
public class Collectionsorting
{
public static void main(String[] args)
{
// Create a list of strings
ArrayList<String> al = new ArrayList<String>();
al.add("Geeks For Geeks");
al.add("Friends");
al.add("Dear");
al.add("Is");
al.add("Superb");
/* Collections.sort method is sorting the
elements of ArrayList in ascending order. */
Collections.sort(al);
// Let us print the sorted list
System.out.println("List after the use of" +
" Collection.sort() :\n" + al);
}
}
输出:
List after the use of Collection.sort() :
[Dear, Friends, Geeks For Geeks, Is, Superb]
按降序排列数组列表
// Java program to demonstrate working of Collections.sort()
// to descending order.
import java.util.*;
public class Collectionsorting
{
public static void main(String[] args)
{
// Create a list of strings
ArrayList<String> al = new ArrayList<String>();
al.add("Geeks For Geeks");
al.add("Friends");
al.add("Dear");
al.add("Is");
al.add("Superb");
/* Collections.sort method is sorting the
elements of ArrayList in ascending order. */
Collections.sort(al, Collections.reverseOrder());
// Let us print the sorted list
System.out.println("List after the use of" +
" Collection.sort() :\n" + al);
}
}
输出:
List after the use of Collection.sort() :
[Superb, Is, Geeks For Geeks, Friends, Dear]
根据用户定义的条件对数组列表进行排序。 我们可以使用比较器接口来达到这个目的。
// Java program to demonstrate working of Comparator
// interface and Collections.sort() to sort according
// to user defined criteria.
import java.util.*;
import java.lang.*;
import java.io.*;
// A class to represent a student.
class Student
{
int rollno;
String name, address;
// Constructor
public Student(int rollno, String name,
String address)
{
this.rollno = rollno;
this.name = name;
this.address = address;
}
// Used to print student details in main()
public String toString()
{
return this.rollno + " " + this.name +
" " + this.address;
}
}
class Sortbyroll implements Comparator<Student>
{
// Used for sorting in ascending order of
// roll number
public int compare(Student a, Student b)
{
return a.rollno - b.rollno;
}
}
// Driver class
class Main
{
public static void main (String[] args)
{
ArrayList<Student> ar = new ArrayList<Student>();
ar.add(new Student(111, "bbbb", "london"));
ar.add(new Student(131, "aaaa", "nyc"));
ar.add(new Student(121, "cccc", "jaipur"));
System.out.println("Unsorted");
for (int i=0; i<ar.size(); i++)
System.out.println(ar.get(i));
Collections.sort(ar, new Sortbyroll());
System.out.println("\nSorted by rollno");
for (int i=0; i<ar.size(); i++)
System.out.println(ar.get(i));
}
}
输出:
Unsorted
111 bbbb london
131 aaaa nyc
121 cccc jaipur
Sorted by rollno
111 bbbb london
121 cccc jaipur
131 aaaa nyc
arrays . sort()vs collections . sort() arrays . sort 适用于也可以是原始数据类型的数组。收藏。sort()适用于对象集合，如数组列表、链接列表等。
在创建给定数组项的数组列表后，我们可以使用 Collections.sort()对数组进行排序。
// Using Collections.sort() to sort an array
import java.util.*;
public class Collectionsort
{
public static void main(String[] args)
{
// create an array of string objs
String domains[] = {"Practice", "Geeks",
"Code", "Quiz"};
// Here we are making a list named as Collist
List colList =
new ArrayList(Arrays.asList(domains));
// Collection.sort() method is used here
// to sort the list elements.
Collections.sort(colList);
// Let us print the sorted list
System.out.println("List after the use of" +
" Collection.sort() :\n" +
colList);
}
}
输出:
List after the use of Collection.sort() :
[Code, Geeks, Practice, Quiz]
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