Built-In Routines for Arrays

The Arrays class (java.util.Arrays) is a set of built-in static methods that are useful when working with arrays. The Arrays class contains built-in methods for searching and sorting, as well as a variety of other methods.

beware There are often built-in sort "routines" in Java compiler packages,
such as Arrays.sort ( ).  It is imperative that you, the programmer, know and understand at least one method of sorting an array, separate from a built in "routine", for test taking purposes. 

• sort (array) - sorts an array into ascending order

Example - Using Arrays.sort( )

// short demo to show built-in sorting routine at work

import java.util.Arrays;  //notice the new required import statement

public class SortTest
{
   public static void main(String[] args)
   {
      //Sorting integers
      int[ ] nums = {12, 18, 7, 20, 11};

      Arrays.sort(nums);  //use built-in sorting method

      for (int i = 0; i < 5; i++)
         System.out.println(nums[ i ]);

      //Sorting strings
      String[ ] people = {"Wally","Henry","Felix","George"};

      Arrays.sort(people);    //use built-in sorting method

      for (int i = 0; i < 4; i++)
         System.out.println(people[ i ]);
   }
}
dragon
Output:
7
11
12
18
20
Felix
George
Henry
Wally

Notice that this built-in routine (shown above) sorts into "ascending" order only.


• binarySearch(array, value) - returns a -1 if the key "value" is not found in the array. The array must first be sorted by the Arrays.sort method.

Example - Using Arrays.binarySearch( )

// short demo to show built-in searching routine at work

import java.util.Arrays;  //notice the new required import statement

public class SearchTest
{
   public static void main(String[] args)
   {
     
    String[ ] people = "Wally","Henry","Felix","George"};

      Arrays.sort(people);   //use built-in sorting method

      for (int i = 0; i < 4; i++)
         System.out.println(people[ i ]);

   //Searching for location of "George" in sorted array
   int index = Arrays.binarySearch(people,"George");

   System.out.println("George located at index "+index);
   }
}
monsterpurple
Output:
Felix
George
Henry
Wally
George located at index 1

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