Bug 13034 Cannot create a Source Folder in a new Java Project
build 20020404 If you try and create a Source Folder in a Java Project you have just created you get an error preventing you from hitting finish. STEPS 1) Create Java Project Foo 2) Open New->Source Folder 3) Enter Bar as the name - you will get "Cannot nest entry Bar inside entry Foo/Bar" 4) Create a folder Bar. 5) Add it as a source folder in the Properties Dialog for Foo. No problem.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/NewSourceFolderWizardPage.java
} else if (field == fProjectField) {
			updateProjectStatus();
			updateRootStatus();
		} else if (field == fEditClassPathField) {
			if (showClassPathPropertyPage()) {
				updateProjectStatus();
				updateRootStatus();
			}
		}
		updateStatus(new IStatus[] { fProjectStatus, fRootStatus });
	}
	
	
	private void updateProjectStatus() {
		fCurrJProject= null;
		
		String str= fProjectField.getText();
		if (str.length() == 0) {
			fProjectStatus.setError(NewWizardMessages.getString("NewSourceFolderWizardPage.error.EnterProjectName")); 
			return;
		}
		IPath path= new Path(str);
		if (path.segmentCount() != 1) {
			fProjectStatus.setError(NewWizardMessages.getString("NewSourceFolderWizardPage.error.InvalidProjectPath")); 
			return;
		}
		IProject project= fWorkspaceRoot.getProject(path.toString());
		if (!project.exists()) {
			fProjectStatus.setError(NewWizardMessages.getString("NewSourceFolderWizardPage.error.ProjectNotExists")); 
			return;