Java/C2/Array-Operations/English-timed
From Script | Spoken-Tutorial
| Time | Narration |
| 00:02 | Welcome to the spoken tutorial on Array Operations in java. |
| 00:07 | In this tutorial, you will learn how to: |
| 00:09 | import the class Arrays and |
| 00:12 | perform basic operations on arrays. |
| 00:15 | For this tutorial, we are using Ubuntu 11.10, JDK 1.6 and Eclipse 3.7.0 |
| 00:25 | For this tutorial, you should have knowledge of arrays in Java. |
| 00:30 | If not, for relevant tutorials, please visit our website which is as shown. [1] |
| 00:35 | The methods for array operations are available in a class called Arrays. |
| 00:40 | To access them, we need to import that class. |
| 00:43 | It is done by the statement import java.util.Arrays semicolon. |
| 00:50 | We can access a method from the class. |
| 00:52 | We do it by adding a 'dot' and the method name. |
| 00:56 | So, Arrays dot toString means toString method from the Arrays class. |
| 01:05 | Now switch to eclipse. |
| 01:08 | We have already created a class ArraysDemo. |
| 01:13 | Let us now import the class Arrays. |
| 01:16 | The import statement is written before the class definition. |
| 01:22 | So, before public class, type: |
| 01:26 | import java.util.Arrays semicolon |
| 01:46 | This statement says that java contains a package called util which contains the class Arrays and it has to be imported. |
| 01:59 | Now, let us add an array. |
| 02:01 | Inside the main function, type: |
| 02:03 | int marks open and close square brackets equal to within curly brackets 2, 7, 5, 4, 8 |
| 02:20 | Now we shall use a method available in the Arrays class to get a string representation of the array and print it. |
| 02:28 | So, type: String mStr equal to Arrays dot toString parentheses inside parentheses will give the array name i.e. marks. |
| 02:50 | Now, this toString method will give the string representation of the array. |
| 02:56 | We shall print the marks. |
| 02:58 | So, type System dot out dot println inside parentheses type mStr; |
| 03:12 | Now, let us look at the output. So save and run the program. |
| 03:18 | As we can see in the output, the toString method has given a string representation of the array. |
| 03:26 | Now, let us look at sorting the elements of the array. |
| 03:31 | So, before the line Arrays dot toString type: Arrays dot sort within parentheses the Array name i.e marks. |
| 03:46 | So, the sort method in the Arrays class sorts the elements of the array passed to it. |
| 03:53 | Now we are sorting the elements of the array marks and then printing the string form of it. |
| 04:04 | Let us look at the output. So save and run. |
| 04:11 | As we can see in the output, the sort method has sorted the array in the ascending order. |
| 04:19 | Note that the sort method has changed the array itself. |
| 04:22 | This type of sorting is called inplace sorting. |
| 04:26 | It means that the array which contains the elements is changed as a result of sorting. |
| 04:33 | The next method we are going to look at is fill. |
| 04:38 | The fill method takes two arguments. |
| 04:43 | Remove the sorting line and |
| 04:50 | type: Arrays dot fill within brackets the name of the array i.e marks; |
| 05:05 | This is our first argument and second is the value that should be filled in the array, we will give it 6 and semicolon. Save and Run. |
| 05:24 | As we can see, as the name goes, the fill method fills the array with the given argument i.e 6. |
| 05:32 | The next method we are going to look at is copyOf. |
| 05:37 | We are going to copy all the elements of the array marks into the array marksCopy. |
| 05:44 | So, remove 'arrays dot fill'. |
| 05:48 | And type: int marksCopy[]; |
| 05:59 | Next line, type: marksCopy = Arrays.copyOf(marks, 5); |
| 06:25 | This method takes two arguments. |
| 06:29 | The first argument is the name of the array from which you want to copy the elements.i.e marks. |
| 06:39 | The second is the no.of elements to copy, over here we will copy 5. |
| 06:47 | Then, in arrays dot toString, change marks to marksCopy. |
| 06:55 | Now save and run the program. |
| 07:01 | We see that the elements of the array marks have been copied to the array marksCopy. |
| 07:10 | Let us see what happens if we change the no.of elements to be copied. |
| 07:15 | Let's Change 5 to 3. |
| 07:19 | Save and Run. |
| 07:24 | As we can see, only the first three elements have been copied. |
| 07:31 | Let us see what happens if the no.of elements to be copied is greater than the total no.of elements in the array. |
| 07:39 | So, change 3 to 8. |
| 07:44 | Save and Run the program. |
| 07:48 | As we can see, the extra elements have been set to the default value which is 0. |
| 07:54 | Next, we'll see how to copy a range of values. |
| 07:58 | So, change copyOf to copyOfRange and 8 to 1, 4. |
| 08:15 | This method copies all the elements starting from the index 1 and stopping at index 3. |
| 08:27 | Save and Run. |
| 08:31 | As we can see, the elements from index 1 to 3 have been copied. |
| 08:39 | Note that we have given 1, 4 as our arguments. |
| 08:47 | But, even then the element at index 4 has not been copied. |
| 08:50 | Only the elements till index 3 have been copied. It stops one index before the given range. |
| 09:01 | So, this behavior ensures that continuity of ranges is maintained. |
| 09:07 | (0, 4) implies from index 0 to 3. |
| 09:12 | (4, 6) will imply index from 4 to 5. |
| 09:17 | So it behaves as if (0, 4) + (4, 6) = (0, 5). |
| 09:26 | This brings us to the end of this tutorial. |
| 09:31 | In this tutorial, we have learnt: |
| 09:33 | How to import the class Arrays. |
| 09:36 | Perform array operations like toStrings, sort, copy, fill. |
| 09:44 | For assignment: |
| 09:46 | Read about the Arrays.equals method and find out what it does. |
| 09:53 | To know more about the Spoken Tutorial project, |
| 09:55 | watch the video available at [2]. |
| 10:02 | It summarizes the Spoken Tutorial project. |
| 10:05 | If you do not have good bandwidth, you can download and watch it. |
| 10:09 | The Spoken Tutorial project team: Conducts workshops using Spoken Tutorials, gives certificates to those who pass an online test. |
| 10:16 | For more details, please write to contact @ spoken HYPHEN tutorial DOT org. |
| 10:22 | Spoken Tutorial project is a part of the Talk to a Teacher project and is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 10:31 | More information on this mission is available at spoken HYPHEN tutorial DOT org SLASH NMEICT HYPHEN Intro. |
| 10:39 | This tutorial has been contributed by TalentSprint. Thanks for joining. |
| 10:43 | This is Prathmesh Salunke, signing off. Jai Hind. |
