Difference between revisions of "Java/C2/Introduction-to-Array/English"

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Line 59: Line 59:
  
  
−
For example, a list of marks, a list of names, a list of temperatures or as shown on the slide, a list of numbers.
+
For example, a list of marks, a list of names, a list of temperatures, a list of rainfall,
  
  
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−
The second element has index 1 and so on.
+
The index of the  second element has index 1 and so on.
  
  
Line 97: Line 97:
  
 
'''int rainfall<nowiki>[] = {25, 31, 29, 13, 27, 35, 12};</nowiki>'''
 
'''int rainfall<nowiki>[] = {25, 31, 29, 13, 27, 35, 12};</nowiki>'''
−
| style="border:1pt solid #000000;padding:0.097cm;"| Inside main function, type
+
| style="border:1pt solid #000000;padding:0.097cm;"| So Inside main function, type
  
  
−
'''int rainfall '''''open close square brackets equal to''''' '''''within curly brackets''''' 25, 31, 29, 13, 27, 35, 12 '''''semicolon.''
+
'''int rainfall '''''open close   brackets equal to''''' '''''within curly brackets type''''' 25, 31, 29, 13, 27, 35, 12 ''''' and finally a semicolon.''
  
  
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The braces are used to specify the elements of the array.
 
The braces are used to specify the elements of the array.
  
−
 
+
let us now access data.
−
Now let us access data.
+
  
 
|-
 
|-
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Highlight as you explain.
 
Highlight as you explain.
−
| style="border:1pt solid #000000;padding:0.097cm;"| Next line, type  
+
| style="border:1pt solid #000000;padding:0.097cm;"| So Next line, type  
  
  
−
'''System '''''dot '''''out '''''dot'' '''println '''within brackets''' rainfall '''then within square brackets 2 semicolon.
+
'''System '''''dot '''''out '''''dot'' '''println ''' ''' rainfall ''' in square brackets type  2 semicolon.
  
  
−
We are printing the element with index 2.
+
We are printing the element with index number  2.
  
  
−
In other words, the third element in the array.
+
In other words, the third element in the array i.e.29.
  
  
−
Let us now run the code.
+
Let us save  run the program
  
 
|-
 
|-
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Highlight the ouput
 
Highlight the ouput
−
| style="border:1pt solid #000000;padding:0.097cm;"| As we can see, the output is the third value, '''29'''.  
+
| style="border:1pt solid #000000;padding:0.097cm;"| As we can see, the output is the third element,i.e '''29'''.  
  
  
−
Now let us try a different index.
+
Now let us type  0 in place  of 2
  
 
|-
 
|-
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save and run. Point to output
 
save and run. Point to output
−
| style="border:1pt solid #000000;padding:0.097cm;"| Change '''2''' to '''0'''
+
| style="border:1pt solid #000000;padding:0.097cm;"| Save and run the program
  
 +
As we can see, the output is the first value  i.e 25
  
−
As we can see, the output is the first value.
 
  
−
 
+
Now let us modify a valueof the first icon
−
Now let us modify a value.
+
  
 
|-
 
|-
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−
| style="border:1pt solid #000000;padding:0.097cm;"| We shall change the value of the first item.
+
| style="border:1pt solid #000000;padding:0.097cm;"| Save
−
 
+
−
 
+
 
Type '''rainfall<nowiki>[0] = 11;</nowiki>'''
 
Type '''rainfall<nowiki>[0] = 11;</nowiki>'''
  
  
−
Now let us see its value.
+
Now let us see its value. So save and run the program
  
  
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|-
 
|-
 
| style="border:1pt solid #000000;padding:0.097cm;"|  
 
| style="border:1pt solid #000000;padding:0.097cm;"|  
−
| style="border:1pt solid #000000;padding:0.097cm;"| Now what if we only know the size of the array and do not know the values.
+
| style="border:1pt solid #000000;padding:0.097cm;"| Now what if we know only the size of the array and do not know the values.
−
 
+
−
 
+
 
Let us see how to create such array.
 
Let us see how to create such array.
  
 
|-
 
|-
−
|  
+
| style="border:1pt solid #000000;padding:0.097cm;"|  
 
|style="border:1pt solid #000000;padding:0.097cm;"| Remove everything in main function and type
 
|style="border:1pt solid #000000;padding:0.097cm;"| Remove everything in main function and type
 
'''int squares<nowiki>[] = </nowiki>new int<nowiki>[10];</nowiki>'''
 
'''int squares<nowiki>[] = </nowiki>new int<nowiki>[10];</nowiki>'''
−
This statement creates an array of 10 inetgers called '''squares.'''
+
This statement creates an array of integers having 10 elements. The name of the array is '''squares'''.
−
Now let us add some values.
+
Now let us add some values to it
  
 
|-
 
|-
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'''squares<nowiki>[3] = 16;</nowiki>'''
 
'''squares<nowiki>[3] = 16;</nowiki>'''
−
| style="border:1pt solid #000000;padding:0.097cm;"| '''Type'''
+
| style="border:1pt solid #000000;padding:0.097cm;"|So  '''Type'''
  
  
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−
We have entered the squares of first four numbers. Now what about the other elements of the array. Let us see what they contain.
+
So We have entered the squares of first four numbers. Now what about the other elements of the array. Let us see what they contain.
  
 
|-
 
|-
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'''System.out.println(squares<nowiki>[5]);</nowiki>'''
 
'''System.out.println(squares<nowiki>[5]);</nowiki>'''
−
| style="border:1pt solid #000000;padding:0.097cm;"| We shall print the sixth value in the array.
+
| style="border:1pt solid #000000;padding:0.097cm;"|So We shall print the sixth value in the array.
  
  
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|-
 
|-
 
| style="border:1pt solid #000000;padding:0.097cm;"| Save and run. Point to output
 
| style="border:1pt solid #000000;padding:0.097cm;"| Save and run. Point to output
−
| style="border:1pt solid #000000;padding:0.097cm;"| We see that the value is zero. This is because when we create an array of integers, all the values are initialized to 0. Similarly an array of floats will have all its values initialized to 0.0.
+
| style="border:1pt solid #000000;padding:0.097cm;"| Save and run the program.We see that the value is zero. This is because when we create an array of integers, all the values are initialized to 0. Similarly an array of floats will have all its values initialized to 0.0.
  
  
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'''int n, x<nowiki>;</nowiki>'''
 
'''int n, x<nowiki>;</nowiki>'''
  
−
'''for(x = 4, x<nowiki> < 10, </nowiki>x = x + 1){'''
+
'''for(x = 4; x<nowiki> < 10; </nowiki>x = x + 1){'''
  
 
'''n = x + 1;'''
 
'''n = x + 1;'''
  
−
'''squares<nowiki>[</nowiki>x] = n * n'''
+
'''squares<nowiki>[</nowiki>x] = n * n;'''
  
 
'''}'''
 
'''}'''
−
| style="border:1pt solid #000000;padding:0.097cm;"| '''Type'''
+
| style="border:1pt solid #000000;padding:0.097cm;"|So '''Type'''
  
  
−
'''int n, x<nowiki>;</nowiki>'''
+
'''int n, x<nowiki>;</nowiki>'''  
  
−
'''for(x = 4, x<nowiki> < 10, </nowiki>x = x + 1){'''
+
'''for(x = 4; x<nowiki> < 10;</nowiki>x = x + 1){'''
  
 
'''n = x + 1;'''
 
'''n = x + 1;'''
  
−
'''squares<nowiki>[</nowiki>x] = n * n'''
+
'''squares<nowiki>[</nowiki>x] = n * n;'''
  
 
'''} '''
 
'''} '''
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|-
 
|-
 
| style="border:1pt solid #000000;padding:0.097cm;"| Save and run. Point to output
 
| style="border:1pt solid #000000;padding:0.097cm;"| Save and run. Point to output
−
| style="border:1pt solid #000000;padding:0.097cm;"| As we can see, the sixth element now is the square of 6, which is 36.
+
| style="border:1pt solid #000000;padding:0.097cm;"| As we can see, we are printing the value of sixth element in  array  SoSave and run. We  see the sixth element is now square of 6, which is 36.
  
  
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−
This way all the elements from index 0 to index 9 are set to the corresponding squares.
+
This way all the elements from index 0 to   9 are set to the corresponding squares.
  
  
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−
change '''5 '''to '''2'''
+
So change '''5 '''to '''2'''
  
  
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−
As we can see, the value of third element has been set in the loop and it is 9.
+
As we can see, the value of the third element has been set in the loop and it is 9.
  
 
|-
 
|-
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| style="border:1pt solid #000000;padding:0.097cm;"| We have come to the end of this tutorial.  
 
| style="border:1pt solid #000000;padding:0.097cm;"| We have come to the end of this tutorial.  
  
−
In this tutorial we have learnt how to '''use for loop in java.'''
+
In this tutorial we have learnt  
−
 
+
TO declare and initialize the array ,
 +
And access element in an array
 
|-
 
|-
 
| style="border:1pt solid #000000;padding:0.097cm;"| Slide 8'''Assignment'''
 
| style="border:1pt solid #000000;padding:0.097cm;"| Slide 8'''Assignment'''

Latest revision as of 10:26, 10 May 2013

Title of script: Introduction to Arrays

Author: TalentSprint

Keywords: arrays, java, video tutorial


Visual Cue Description
Slide 1

Welcome

Welcome to the spoken tutorial on Introduction to Arrays.
Slide 2

Learning Outcomes

In this tutorial, you will learn how
  • to create arrays and
  • access elements in arrays.


Slide 3

Tools Used

For this tutorial we are using
  • Ubuntu 11.10
  • JDK 1.6 and
  • Eclipse 3.7.0


Slide 4

Prerequisites

For this tutorial, you should have knowledge of data types and for loop in Java.


If not, for relevant tutorial please visit our website which as shown.

Slide 5 and 6

Arrays


Highlight index column as you explain.

Arrays are a collection of data.


For example, a list of marks, a list of names, a list of temperatures, a list of rainfall,


Each item has an index based on its position.


The index of the first element is 0.


The index of the second element has index 1 and so on.


Let us now see how to store this data.


So switch to Eclipse.

Minimize Slides and open Eclipse

Eclipse should contain the following code

public class ArraysDemo{

public static void main(String[] args){

}

}

A class named ArraysDemo has already been created.


Within the main method, let us add the rainfall data.

Inside main function, type

int rainfall[] = {25, 31, 29, 13, 27, 35, 12};

So Inside main function, type


int rainfall open close brackets equal to within curly brackets type 25, 31, 29, 13, 27, 35, 12 and finally a semicolon.


Note the square braces after the variable name rainfall.


This declares rainfall as an array of integers.


The braces are used to specify the elements of the array. 

let us now access data.
In the next line, type

System.out.println(rainfall[2]);


Highlight as you explain.

So Next line, type


System dot out dot println rainfall in square brackets type 2 semicolon.


We are printing the element with index number 2.


In other words, the third element in the array i.e.29.


Let us save run the program

Save and run.


Highlight the ouput

As we can see, the output is the third element,i.e 29.


Now let us type 0 in place of 2

Change rainfall[2] to rainfall[0]


save and run. Point to output

Save and run the program

As we can see, the output is the first value i.e 25


Now let us modify a valueof the first icon

Before the Syste... line, type

rainfall[0] = 11;


save and run. Point to output


Save

Type rainfall[0] = 11;


Now let us see its value. So save and run the program


As we can see, the value has been changed to 11.

Now what if we know only the size of the array and do not know the values.

Let us see how to create such array.

Remove everything in main function and type

int squares[] = new int[10]; This statement creates an array of integers having 10 elements. The name of the array is squares. Now let us add some values to it

In the next line, type

squares[0] = 1;

squares[1] = 4;

squares[2] = 9;

squares[3] = 16;

So Type


squares[0] = 1;

squares[1] = 4;

squares[2] = 9;

squares[3] = 16;


So We have entered the squares of first four numbers. Now what about the other elements of the array. Let us see what they contain.

In the next line, type

System.out.println(squares[5]);

So We shall print the sixth value in the array.


Type System.out.println(squares[5]);



Save and run. Point to output Save and run the program.We see that the value is zero. This is because when we create an array of integers, all the values are initialized to 0. Similarly an array of floats will have all its values initialized to 0.0.


It would be a long process if we have to type each value into the array. Instead, let us use a for loop.

After the squares[3] line, type

int n, x;

for(x = 4; x < 10; x = x + 1){

n = x + 1;

squares[x] = n * n;

}

So Type


int n, x;

for(x = 4; x < 10;x = x + 1){

n = x + 1;

squares[x] = n * n;

}


We iterate over numbers from 4 to 9 and set the corresponding element in the array.


Now let us see the output.

Save and run. Point to output As we can see, we are printing the value of sixth element in array SoSave and run. We see the sixth element is now square of 6, which is 36.


In fact now we can set all the values inside the for loop.

Remove all the lines from

squares[0]... to squares[3]...


Change x = 4 to x = 0


Change println(squares[5]) to

println(squares[2])


save and run. Point to output

Remove the lines that set the values manually and change 4 to 0


This way all the elements from index 0 to 9 are set to the corresponding squares.


We shall now see the value of the third element.


So change 5 to 2


Save and run


As we can see, the value of the third element has been set in the loop and it is 9.

This way, arrays can be created and used.
Minimize the Eclipse window and switch to slides.


Slide 7

Summary

We have come to the end of this tutorial.

In this tutorial we have learnt TO declare and initialize the array , And access element in an array

Slide 8Assignment The assignment for this tutorial is,


Given an array of integers, find the sum of all the elements in the array.

Slide 9About the Spoken Tutorial Project
  • It summarises the Spoken Tutorial project
  • If you do not have good bandwidth, you can download and watch it


To know more about the Spoken Tutorial project, watch the video available at the following link. It summarises the project.If you do not have good bandwidth, you can download and watch it.
Slide 10Spoken Tutorial WorkshopsThe Spoken Tutorial Project Team
  • Conducts workshops using spoken tutorials
  • Gives certificates for those who pass an online test


The Spoken Tutorial Project Team. Conducts workshops using spoken tutorials and gives certificates for those who pass an online test. For more details, please write to contact AT spoken HYPHEN tutorial DOT org.
Slide 11Acknowledgement
  • Spoken Tutorial Project is a part of the Talk to a Teacher project
  • It is supported by the National Mission on Education through ICT, MHRD, Government of India
  • More information on this Mission is available at


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. More information on this Mission is available at spoken HYPHEN tutorial DOT org SLASH NMEICT HYPHEN Intro
Slide 12About the contributor
  • This script has been contributed by TalentSprint
  • www.talentsprint.com
  • Thanks for joining


This script has been contributed by TalentSprint.

This is Prathamesh Salunke signing off. Thanks for joining.



Contributors and Content Editors

Arya Ratish, Pratham920, Sneha

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