Java中的Arrays.sort()用法示例

sort()方法是java.util.Arrays类方法。

语法如下：

public static void sort(int[] arr, int from_Index, int to_Index)

arr - the array to be sorted
from_Index - the index of the first element, inclusive, to be sorted
to_Index - the index of the last element, exclusive, to be sorted

This method doesn't return any value.

一个Java程序按升序对整数数组进行排序.

//A sample Java program to sort an array of integers
//using Arrays.sort(). It by default sorts in
//ascending order
import java.util.Arrays;
  
public class SortExample
{
     public static void main(String[] args)
     {
         //Our arr contains 8 elements
         int [] arr = { 13 , 7 , 6 , 45 , 21 , 9 , 101 , 102 };
  
         Arrays.sort(arr);
  
         System.out.printf( "Modified arr[] : %s" , Arrays.toString(arr));
     }
}

输出如下：

Modified arr[] : [6, 7, 9, 13, 21, 45, 101, 102]

我们还可以使用sort()对arr[]的子数组进行排序

//A sample Java program to sort a subarray
//using Arrays.sort().
import java.util.Arrays;
  
public class SortExample
{
     public static void main(String[] args)
     {
         //Our arr contains 8 elements
         int [] arr = { 13 , 7 , 6 , 45 , 21 , 9 , 2 , 100 };
  
         //Sort subarray from index 1 to 4, i.e., //only sort subarray {7, 6, 45, 21} and
         //keep other elements as it is.
         Arrays.sort(arr, 1 , 5 );
  
         System.out.printf( "Modified arr[] : %s" , Arrays.toString(arr));
     }
}

输出如下：

Modified arr[] : [13, 6, 7, 21, 45, 9, 2, 100]

我们还可以按降序排序。

//A sample Java program to sort a subarray
//in descending order using Arrays.sort().
import java.util.Arrays;
import java.util.Collections;
  
public class SortExample
{
     public static void main(String[] args)
     {
         //Note that we have Integer here instead of
         //int[] as Collections.reverseOrder doesn't
         //work for primitive types.
         Integer[] arr = { 13 , 7 , 6 , 45 , 21 , 9 , 2 , 100 };
  
         //Sorts arr[] in descending order
         Arrays.sort(arr, Collections.reverseOrder());
  
         System.out.printf( "Modified arr[] : %s" , Arrays.toString(arr));
     }
}

输出如下：

Modified arr[] : [100, 45, 21, 13, 9, 7, 6, 2]

我们还可以按字母顺序对字符串进行排序。

//A sample Java program to sort an array of strings
//in ascending and descending orders using Arrays.sort().
import java.util.Arrays;
import java.util.Collections;
  
public class SortExample
{
     public static void main(String[] args)
     {
         String arr[] = { "practice.lsbin.org" , "quiz.lsbin.org" , "code.lsbin.org"
                        };
  
         //Sorts arr[] in ascending order
         Arrays.sort(arr);
         System.out.printf( "Modified arr[] : \n%s\n\n" , Arrays.toString(arr));
  
         //Sorts arr[] in descending order
         Arrays.sort(arr, Collections.reverseOrder());
  
         System.out.printf( "Modified arr[] : \n%s\n\n" , Arrays.toString(arr));
     }
}

输出如下：

Modified arr[] : 


Modified arr[] : 
[quiz.lsbin.org, practice.lsbin.org, code.lsbin.org]

我们还可以根据用户定义的标准对数组进行排序。

我们用Comparator接口实现此目的。下面是一个例子。

//Java program to demonstrate working of Comparator
//interface
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)
     {
         Student [] arr = { new Student( 111 , "bbbb" , "london" ), new Student( 131 , "aaaa" , "nyc" ), new Student( 121 , "cccc" , "jaipur" )};
  
         System.out.println( "Unsorted" );
         for ( int i= 0 ; i<arr.length; i++)
             System.out.println(arr[i]);
  
         Arrays.sort(arr, new Sortbyroll());
  
         System.out.println( "\nSorted by rollno" );
         for ( int i= 0 ; i<arr.length; i++)
             System.out.println(arr[i]);
     }
}

输出如下：

Unsorted
111 bbbb london
131 aaaa nyc
121 cccc jaipur

Sorted by rollno
111 bbbb london
121 cccc jaipur
131 aaaa nyc

Arrays.sort()与Collections.sort()

Arrays.sort也适用于具有基本数据类型的数组。Collections.sort()适用于ArrayList、LinkedList等对象集合。