Java中的Arrays.sort()用法示例 _JavaArrays.sort

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 sortedThis 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：