Difference between revisions of "Java/C2/Array-Operations/English-timed"

| Welcome to the spoken tutorial on '''Array Operations''' in java.

| In this tutorial, you will learn how to:

| '''import''' the '''class''' '''Arrays ''' and  

| perform basic operations on '''arrays'''.

|  For this tutorial, we are using '''Ubuntu 11.10''', '''JDK 1.6''' and '''Eclipse 3.7.0'''

| For this tutorial, you should have knowledge of '''arrays''' in Java.

| If not, for relevant tutorials, please visit our website which is as shown. [http://spoken-tutorial.org]

|  The methods for array operations are available in a '''class''' called '''Arrays'''.  

| To access them, we need to '''import''' that '''class'''.

| It is done by the statement '''import java.util.Arrays''' semicolon.

| We can access a '''method''' from the '''class'''.

| We do it by adding a 'dot' and the '''method''' name.

| So, '''Arrays''' dot '''toString''' means '''toString''' method from the  '''Arrays''' '''class'''.

| 01:05

| Now switch to '''eclipse'''.

| Let us now '''import''' the '''class''' '''Arrays'''.

| The '''import''' statement is written before the '''class''' definition.

|So, before '''public class''', type:

|'''import java.util.Arrays''' semicolon

|This statement says that '''java''' contains a '''package''' called '''util''' which contains the class '''Arrays''' and it has to be imported.

| Now, let us add an '''array.'''

|Inside the '''main''' function, type:

|'''int marks''' open and close square brackets equal to within curly brackets '''2, 7, 5, 4, 8 '''  

|Now we shall use a method available in the '''Arrays''' '''class''' to get a string representation of the '''array''' and print it.

|So, type: '''String mStr''' equal to ''' Arrays''' dot ''toString'' parentheses inside parentheses  will give the array name i.e. '''marks'''.

|Now, this '''toString''' method will give the '''string''' representation of the array.

| We shall print the marks.

|So, type '''System ''' dot '''out''' dot '''println''' inside parentheses type '''mStr;'''

|Now, let us look at the output. So '''save''' and '''run''' the program.

| As we can see in the output, the '''toString''' '''method''' has given a string representation of the '''array.'''

|Now, let us look at sorting the elements of the '''array'''.

| So, before the line '''Arrays''' dot '''toString''' type: '''Arrays''' dot '''sort''' within parentheses the Array name i.e '''marks'''.

|So, the '''sort''' '''method''' in the '''Arrays class''' sorts the elements of the '''array''' passed to it.

|Now we are sorting the elements of the array '''marks''' and then printing the '''string''' form of it.

|Let us look at the output. So '''save''' and '''run'''.

|  As we can see in the output, the '''sort''' '''method''' has sorted the '''array''' in the ascending order.

|Note that the '''sort''' '''method''' has changed the '''array''' itself.

|This type of sorting is called '''inplace sorting'''.  

|The next '''method''' we are going to look at is '''fill'''.

|  The '''fill''' '''method''' takes two '''argument'''s.  

|type: '''Arrays''' dot '''fill''' within brackets the name of the array i.e '''marks;'''

|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'''.

|  As we can see, as the name goes, the '''fill''' '''method''' fills the array with the given argument i.e 6.

|The next method we are going to look at is '''copyOf'''.

| We are going to copy all the elements of the array '''marks''' into the array '''marksCopy'''.

|So, remove 'arrays dot fill'.

| And type: '''int marksCopy[];'''

| Next line, type: '''marksCopy = Arrays.copyOf(marks, 5);'''

|This method takes two '''arguments'''.  

|The first '''argument''' is the name of the  array from which you want to copy the elements.i.e '''marks'''.

|  The second is the no.of elements to copy, over here we will copy 5.

|Then, in '''arrays''' dot '''toString''', change '''marks''' to '''marksCopy'''.

|  Now '''save''' and '''run''' the program.

|Let's Change '''5''' to '''3'''.

| '''Save''' and '''Run'''.  

|  So, change '''3''' to '''8'''.

|'''Save''' and '''Run''' the program.

|As we can see, the extra elements have been set to the default value which is 0.

|Next, we'll see how to copy a range of values.

|  So, change '''copyOf''' to '''copyOfRange''' and '''8''' to '''1, 4'''.

|  This '''method''' copies all the elements starting from  the index 1 and stopping at index 3.

| '''Save''' and '''Run'''.  

|Note that we have given 1, 4  as our '''arguments'''.

|But, even then the element at index 4 has not been copied.

|Only the elements till index 3 have been copied. It stops one index before the given range.

| So, this behavior ensures that continuity of ranges is maintained.

|(0, 4) implies from index 0 to 3.

|(4, 6) will imply index from 4 to 5.

|So it behaves as if (0, 4) + (4, 6) = (0, 5).

|  This brings us to the end of this tutorial.  

|In this tutorial, we have learnt:

|How to '''import''' the '''class''' '''Arrays'''.

|Perform array operations like  '''toStrings''', '''sort''', '''copy''', '''fill'''.

| For assignment:

| Read about the '''Arrays.equals''' method and find out what it does.

|To know more about the Spoken Tutorial project,  

|watch the video available at [http://spoken-tutorial.org/What_is_a_Spoken_Tutorial].  

| It summarizes the Spoken Tutorial project.

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|This is Prathmesh Salunke, signing off. Jai Hind.