Java/C2/Introduction-to-Array/English-timed
From Script | Spoken-Tutorial
| Time | Narration |
| 00:02 | Welcome to the spoken tutorial on Introduction to Arrays. |
| 00:07 | In this tutorial, you will learn how to create arrays and access elements in arrays. |
| 00:14 | 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 data types and for loop in Java. |
| 00:32 | If not, for relevant tutorials, please visit our website which is as shown. |
| 00:38 | Arrays are a collection of data. |
| 00:40 | For example, a list of marks, a list of names, a list of temperatures, a list of rainfall. |
| 00:47 | Each item has an index, based on its position. |
| 00:52 | The index of the first element is 0. |
| 00:55 | The index of the second element is 1 and so on. |
| 00:59 | Let us now see how to store this data. |
| 01:03 | So switch to Eclipse. |
| 01:06 | A class named ArraysDemo has already been created. |
| 01:11 | Within the main method, let us add the rainfall data. |
| 01:16 | So, inside main function, type: |
| 01:18 | int rainfall open and close square brackets equal to within curly brackets type 25, 31, 29, 13, 27, 35, 12 and finally the semicolon. |
| 01:53 | Note that the square braces after the variable name rainfall. |
| 01:58 | This declares rainfall as an array of integers. |
| 02:03 | The braces are used to specify the elements of the array. |
| 02:09 | Let us now access data. |
| 02:12 | So on the next line, type: |
| 02:14 | System dot out dot println rainfall in square brackets type 2. |
| 02:28 | We are printing the element with the index number 2. |
| 02:32 | In other words, the third element in the array i.e. 29. |
| 02:38 | Let us save and run the program. |
| 02:43 | As we can see, the output is the third element, i.e 29. |
| 02:49 | Now, let us type 0 in place of 2. |
| 02:56 | Save and run the program. |
| 03:00 | As we can see, the output is the first value i.e 25. |
| 03:07 | Now, let us modify the value of the first item. |
| 03:13 | So, type: rainfall[0] = 11; |
| 03:27 | Now, let us see its value. So save and run the program. |
| 03:34 | As we can see, the value has been changed to 11. |
| 03:40 | Now, what if we know only the size of the array and do not know the values. |
| 03:45 | Let us see how to create such array. |
| 03:49 | Remove everything in main function and type: |
| 03:57 | int squares[] = new int[10]; |
| 04:19 | This statement creates an array of integers having 10 elements. The name of the array is squares. |
| 04:30 | Now, let us add some values to it. |
| 04:33 | So, type: |
| 04:35 | squares[0] = 1; |
| 04:43 | Next line, squares[1] = 4; |
| 04:53 | Next line, squares[2] = 9; |
| 05:04 | squares[3] = 16; |
| 05:15 | So, we have entered the squares of first four numbers. |
| 05:20 | Now what about the other elements of the array. Let us see what they contain. |
| 05:26 | So, we shall print the sixth value in the array. |
| 05:30 | Type: System S capital .out.println(squares[5]); |
| 05:56 | Save and run the program. We see that the value is zero. |
| 06:05 | This is because when we create an array of integers, all the values are initialized to 0. |
| 06:11 | Similarly, an array of floats will have all its values initialized to 0.0. |
| 06:18 | It would be a long process if we have to type each value into the array. Instead, let us use a for loop. |
| 06:28 | So, type:
int n, x ; for(x = 4; x < 10; x = x + 1){ n = x + 1; squares[x] = n * n; } |
| 07:25 | So, we iterate over numbers from 4 to 9 and set the corresponding element in the array. |
| 07:36 | Now, let us see the output. |
| 07:38 | As we can see, we are printing the value of sixth element in array. So, Save and run. |
| 07:52 | We see the sixth element is now square of 6 which is 36. |
| 07:57 | In fact, now we can set all the values inside the for loop. |
| 08:03 | Remove the lines that set the values manually and change 4 to 0. |
| 08:14 | This way, all the elements from index 0 to 9 are set to the corresponding squares. |
| 08:21 | We shall now see the value of the third element. |
| 08:25 | So, change 5 to 2. |
| 08:30 | Save and run. |
| 08:35 | As we can see, the value of the third element has been set in the loop and it is 9. |
| 08:42 | This way, arrays can be created and used. |
| 08:50 | We have come to the end of this tutorial. |
| 08:53 | In this tutorial, we have learnt: |
| 08:55 | To declare and initialize an array. |
| 08:58 | And access an element in an array. |
| 09:01 | The assignment for this tutorial is: |
| 09:04 | Given an array of integers, find the sum of all the elements in the array. |
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| 09:57 | This script has been contributed by TalentSprint.
This is Prathamesh Salunke, signing off. Thanks for joining. |
