Java.util.Arrays.sort() Method

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Description

The java.util.Arrays.(T[] a, int fromIndex, int toIndex, Comparator<? super T> c) method Sorts the specified range of the specified array of objects according to the order induced by the specified comparator. The range to be sorted extends from index fromIndex, inclusive, to index toIndex, exclusive. (If fromIndex==toIndex, the range to be sorted is empty.) All elements in the range must be mutually comparable by the specified comparator (that is, c.compare(e1, e2) must not throw a ClassCastException for any elements e1 and e2 in the range).

This sort is guaranteed to be stable: equal elements will not be reordered as a result of the sort.

The sorting algorithm is a modified mergesort (in which the merge is omitted if the highest element in the low sublist is less than the lowest element in the high sublist). This algorithm offers guaranteed n*log(n) performance.

Declaration

Following is the declaration for java.util.Arrays.sort() method

public static <T> void sort(T[] a, int fromIndex, int toIndex, Comparator<? super T> c)

Parameters

• a − This is the array to be sorted.

• fromIndex − the index of the first element (inclusive) to be sorted

• toIndex − the index of the last element (exclusive) to be sorted

• c − the comparator to determine the order of the array. A null value indicates that the elements' natural ordering should be used.

Return Value

This method does not return any value.

Exception

• ClassCastException − If the array contains elements that are not mutually comparable using the specified comparator.

• IllegalArgumentException − if fromIndex > toIndex

• ArrayIndexOutOfBoundsException − if fromIndex < 0 or toIndex > a.length

Example

The following example shows the usage of java.util.Arrays.sort() method.

package com.tutorialspoint;

import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;

public class ArrayDemo {
   public static void main(String[] args) {

      // initializing unsorted short array
      Short sArr[] = new Short[]{3, 13, 1, 9, 21};

      // let us print all the elements available in list
      for (short number : sArr) {
         System.out.println("Number = " + number);
      }

      // create a comparator
      Comparator<Short> comp = Collections.reverseOrder();

      // sorting array with reverse order using comparator from 0 to 2
      Arrays.sort(sArr, 0, 2, comp);

      // let us print all the elements available in list
      System.out.println("short array with some sorted values(1 to 4) is:");
      for (short number : sArr) {
         System.out.println("Number = " + number);
      }
   }
}

Let us compile and run the above program, this will produce the following result −

Number = 3
Number = 13
Number = 1
Number = 9
Number = 21
short array with some sorted values(1 to 4) is:
Number = 13
Number = 3
Number = 1
Number = 9
Number = 21