Arrays

If you have a long list of integers (or any data type) and need to sort it, use a sort() method of the class Arrays.

Carefully notice the "s" at the end of this class.

Here is a short demo program that shows this with integers:

import java.util.*;

public class ArraysTester
{
  
  public static void main ( String[] args )
  {
    int[] values = { 23, 12, 4, 56, 10, 34, 9, 14, 4, 21, -9, 34, 78, 2, 5, 8 };
    
    // print out the array
    System.out.println("Before: "); 
    for ( int val : values )
      System.out.print( val + ", " ); 
    
    // sort the array
    Arrays.sort( values );
  
    // print out the array
    System.out.println("\nAfter: "); 
    for ( int val : values )
      System.out.print( val + ", " ); 
    System.out.println( );
 
   }
}

The Arrays class has many methods that manipulate arrays. It has methods to search, to copy, to copy a range, to compare arrays, and others. In particular, it has methods to sort an array of byte, char, float, double, int, long, and Object.

The sorting methods are faster than the N2 simple sorts. The time that Arrays.sort() takes for an array of int is proportional to N*log(N) .

On my computer (five years old, home-built) Arrays.sort() sorted an array of 500000 ints in less than a second. Recall that it took 204 seconds with insertion sort.