Difference between revisions of "Java/C2/Errors-and-Debugging-in-Eclipse/English-timed"

|  Welcome to the  tutorial on '''Errors and Debugging using Eclipse.'''

| In this tutorial,we are going to learn  

|what are the possible error  while writing a simple '''Java '''Program,  

|how to identify those errors and rectify them using eclipse.

| For this tutorial we are using  

 

Ubuntu 11.10 and

 

Eclipse 3.7

| To follow this tutorial you must know  

|how to create and run a '''Java Program '''in '''Eclipse.'''

 

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

|   00:41

| In a simple  '''Java program''', the  typical errors could be.

| Mis-match of filename and classname and

|And Typing the print statement in lower-case

|We shall write a program and then make each of these errors and see what happens in '''Eclipse'''

|   Here we have the Eclipse IDE and the project used for the''' HelloWorld''' tutorial   

|We shall  create  a new  class in the project and use it '''New''' Class'''. Let us name the class ''' Error Free''' and select methods stubs '''public static Void main'''

| Let us minimise the package explorer. Remove the comments and add the print statement to the few errors  

|In this case, the '''System.out.println   ''' line has an errors and hence their is the '''red cross mark''' on the left.

|   The list of errors is displayed by hovering the mouse over the '''cross mark.'''

| The first error displayed is syntax error insert  semi-colon to complete block statements  

| notice that once we   add the semi-colon and save the file, the first error is gone.

| | their is only one error now which says;''' hello world cannot be resolved to a variable, which means to display any message on the console the message has to be included in double quotes.

|  Let us add double quotes before and after the message,  

|''' Ctrl''' s''' to '''Save'''. We see that the red cross mark have gone an  d the program is error free. So let us ''' run''' the program and see what happens.

|  Run as '''Java applications''  

 

|   We see that the message has been printed on the console.

|It happens due to a mismatch of '''file name''' and '''class name.'''

 

|It does not  happens usually on '''Eclipse.'''

 

|This is because we use the New Class wizard to create a file and eclipse

 

|creates a file automatically

|  But if we create a '''Java file''' outside of '''Eclipse''' and add it to a project, their is the chance of the error  

 

|So let us stimulate the error , by changing  the class name.

 

 

| 04:59

| Since Java is case-sensitive, now the class name and file name do not match .  

 

| 05:09

|   Notice that , there is a '''red cross mark '''on the left margin.

| 05:14

|   And error message reads '''The public type errorfree must be defined in its own file.

 

 

| 05:20

| | '''Also notice that the word '''errorfree'''is ''' underlined in red colour.

|  ''' Java offers intelligent fixes and we have 2 fixes available here   

 

 

|  The first one is '''rename compilation unit to errorfree java'''

| The second one is   ''''rename  the type to error'''.  

|   The fix that we are looking to is the second one.And we see that once you rename the file the class back to errorfree the error here is missing.

 

| The next error happens due to typing mistakes in the print statement.

 

|  We notice that their is the ''' red-cross mark'''   

 

| And error message reads  '''system cannot be resolved.'''

 

|This means, Java is expecting a class or object or a  variable by the name '''system.'''

 

|But there is nothing like system object   in the code.

 

|   So let us look at the possible fixes..

| there are '''11 fixes ''' out of these, fix that we are looking for is the eighth option

 

 

| '''Change to 'System' (java.lang)'''

 

|You can see that once we change it to capital S the error is missing.

|  here is  how you identify errors in Java using eclipse and rectify them   

|In this tutorial we have seen

|'''what are the typical errors while writing a Java program''' and  

|how to '''identify them and rectify them using Eclipse'''.

|  | As an assignment for this tutorial,  find out the error in the code given below and fix them

| 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

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| 08:11

|It is supported by the '''National Mission on Education through ICT, MHRD, Government of India. '''

 

| 08:17

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|     08:23

 

 

 

 

|}