Description: Eclipse can not build the project, because  project is missing default builder.  It happens most of the time when checking out project from SVN or CVS.

Solution:  You need to add the default Java builder into .project file.

Verify that following lines are present in .project file of the eclipse project. If it is not present in the file, copy it from here and save the file.

Adding default Java builder


<buildSpec>
<buildCommand>
<name>org.eclipse.jdt.core.javabuilder</name>
<arguments>
</arguments>
</buildCommand>
</buildSpec>
<natures>
<nature>org.eclipse.jdt.core.javanature</nature>
</natures>


That’s it! select the Java builder from project propertiese > builder, clean and build the project again. you should be able to build the project now.

Problem Whenever I replace any jar file in workspace, eclipse shows error
An internal error occurred during updating JSP index

Solution the only solution I know so far is, restart eclipse workspace.

Unable to install break points in eclipse.
This is a very common error with eclipse. When you try to set a break point, eclipse says “unable to install breakpoint due to missing line number attributes”.

Description of the error

Can not set the break point. A dialog box appears with the error message like

Unable to install breakpoint in xyz class due to missing line number attributes. modify compiler options to generate line number attributes.

Reason: Absent line number attributes in generated class file.

Solution
Follow this steps if you are compiling classes using eclipse

1. If you are compiling using the eclipse. Verify the class file generation options.

Go to windows > preferences > Java > compiler screen.

Make sure that add line number attributes to generated files (used by debugger) check box is checked.

If you don’t know, what other options are. Check all other three check boxes also.

Eclipse - preferences

Follow this steps if you are compiling using ANT

Look into the build file and make sure that debug attribute is set to true in javac task

<javac  debug=”true” srcdir=”" destdir=”">

Set debug=”true” and build again.

<javac srcdir=”"  destdir=”" verbose=”false” debug=”true” debuglevel=”lines,vars,source”>

That’s it !! Try setting the break point again.