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'''s while writing a simple '''Java '''program,  

|how to identify those '''error'''s 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]

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

| Mis-match of 'file name' and 'class name' 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 ''' ErrorFree''' and select '''methods stubs''' '''public static void main'''.

| Let us minimize the package explorer. Remove the comments and add the print statement with a few errors.

|In this case, the '''System.out.println''' line has an error and hence there is a '''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 semicolon and save the file, the first error is gone.

|There is only one error now which says: '''Helloworld 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 is gone and the program is error free. So, let us '''run''' the program and see what happens.

|  '''Run as''' > '''Java application'''  

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

|It does not  happen 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, there is a chance of the error.

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

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

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

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

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

|  '''Eclipse''' 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 errorfree'''.  

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

|  We notice that there 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, the 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 errors in the code given below and fix them.

| watch the video available at the following link. It summarizes the project.  

|If you do not have good bandwidth, you can download and watch it.

|  The Spoken Tutorial Team conducts workshops using spoken tutorials.

|Gives certificates for those who pass an online test. For more details, please write to  '''contact AT spoken HYPHEN tutorial DOT org.'''

|  Spoken Tutorial Project is a part of the Talk to a Teacher project.

| 08:11

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

| 08:17

|More information on this mission is available at '''spoken HYPHEN tutorial DOT org SLASH NMEICT HYPHEN Intro'''

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