File <-> IFile

Convert.java

//File > IFile：
      IContainer[] findContainersForLocationURI = ResourcesPlugin.getWorkspace().getRoot().findContainersForLocationURI(
                file.toURI());
        IFile[] findFilesForLocationURI = ResourcesPlugin.getWorkspace().getRoot().findFilesForLocationURI(filefile.toURI());



//IFile > File:

IProject fsProject = ResourceModelUtils.getProject(project);
IFolder tmpFolder = ResourceUtils.getFolder(fsProject, RepositoryConstants.TEMP_DIRECTORY, true);
String tmpFilename = "DOC" + documentationItem.getProperty().getId();

IFile fileTmp = tmpFolder.getFile(tmpFilename);//Get IFile reference by file name;
File file = fileTmp.getLocation().toFile(); //Get File reference by IFile reference.
File newFile = new File(fileTmp.getLocation().toOSString()); //Convert IFile to File.