// create the manager and bind to a widget
ResourceManager resManager =
    new LocalResourceManager(JFaceResources.getResources(), composite);

// create resources
Color color = resManager.createColor(new RGB(200, 100, 0));
Font font = resManager.
    createFont(FontDescriptor.createFrom("Arial", 10, SWT.BOLD));
// get an imageDescriptor and create Image object
Image image = resManager.createImage(imageDescriptor);

Bundle bundle = FrameworkUtil.getBundle(this.getClass());
// use the org.eclipse.core.runtime.Path as import
URL url = FileLocator.find(bundle,
    new Path("icons/alt_window_32.gif"), null);
ImageDescriptor imageDescriptor = ImageDescriptor.createFromURL(url);

public class ResourceUsingLabelProvider extends LabelProvider {

    private ResourceManager resourceManager = new LocalResourceManager(JFaceResources.getResources());

    @Override
    public Image getImage(Object element) {
        if (element instanceof Task) {
            Bundle bundle = FrameworkUtil.getBundle(this.getClass());
            // use the org.eclipse.core.runtime.Path as import
            URL url = FileLocator.find(bundle, new Path("icons/task.png"), null);
            ImageDescriptor imageDescriptor = ImageDescriptor.createFromURL(url);

            // return the image being created by the resourceManager
            return resourceManager.createImage(imageDescriptor);
        }

        return super.getImage(element);
    }

    @Override
    public void dispose() {
        super.dispose();

        // dispose the ResourceManager yourself
        resourceManager.dispose();
    }
}

// create here a text widget

Text text= ...

// create the decoration for the text UI component
ControlDecoration deco =  new ControlDecoration(text, SWT.TOP | SWT.RIGHT);

// re-use an existing image
Image image = FieldDecorationRegistry.
    getDefault().
    getFieldDecoration(FieldDecorationRegistry.DEC_INFORMATION).
    getImage();
// set description and image
deco.setDescriptionText("This is a tooltip text");
deco.setImage(image);
// hide deco if not in focus
deco.setShowOnlyOnFocus(true);

//hide the decoration if the text widget has content
text.addModifyListener(e -> {
    Text source = (Text) e.getSource();
    if (!source.getText().isEmpty()) {
        deco.hide();
    } else {
        deco.show();
    }
});

deco.hide();
deco.show();

import static org.eclipse.jface.layout.GridDataFactory.fillDefaults;
import static org.eclipse.jface.widgets.WidgetFactory.text;

parent.setLayout(new GridLayout(2, false));

text = text(SWT.BORDER).message("Enter City")
        .layoutData(fillDefaults()
        .grab(true, false).create())
        .create(parent);

// Define field assists for the text widget
// use "." and " " activate the content proposals
char[] autoActivationCharacters = new char[] { '.', ' ' };
KeyStroke keyStroke;
try {
    keyStroke = KeyStroke.getInstance("Ctrl+Space");
    new ContentProposalAdapter(text, new TextContentAdapter(),
    new SimpleContentProposalProvider("ProposalOne", "ProposalTwo", "ProposalThree"),
    keyStroke, autoActivationCharacters);
} catch (ParseException e1) {
    e1.printStackTrace();
}

package com.vogella.eclipse.viewer;

public class Person {
    private String firstName;
    private String lastName;
    private boolean married;

    public Person(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public boolean isMarried() {
        return married;
     }

    public void setMarried(boolean married) {
        this.married = married;
    }
}

// the following code is executed by the method which
// creates the user interface
// assumes parent is an SWT Composite

GridLayout layout = new GridLayout(2, false);
parent.setLayout(layout);


Label label = new Label(parent, SWT.NONE);
label.setText("Select a person:");
final ComboViewer viewer = new ComboViewer(parent, SWT.READ_ONLY);

// the ArrayContentProvider object does not store any state,
// therefore, you can re-use instances

viewer.setContentProvider(ArrayContentProvider.getInstance());
viewer.setLabelProvider(new LabelProvider() {
    @Override
    public String getText(Object element) {
        if (element instanceof Person) {
            Person person = (Person) element;
            return person.getFirstName();
        }
        return super.getText(element);
    }
});

List<Person> persons = Arrays.asList(new Person("Lars", "Vogel"),
        new Person("Tim", "Taler"), new Person("Jim", "Knopf"));

// set the input of the Viewer,
// this input is send to the content provider
// must be called after setContentProvider

viewer.setInput(persons);


//react to the selection change of the viewer
//note that the viewer returns the actual object 

viewer.addSelectionChangedListener(new ISelectionChangedListener() {
    @Override
    public void selectionChanged(SelectionChangedEvent event) {
        IStructuredSelection selection = (IStructuredSelection) event
            .getSelection();
        if (selection.size() > 0){
            System.out.println(((Person) selection.getFirstElement())
                    .getLastName());
        }
    }
});

// you can select an object directly via the domain object
Person person = persons[0];
viewer.setSelection(new StructuredSelection(person));

// retrieves the selection, returns the data model object
IStructuredSelection selection = viewer.getStructuredSelection();
Person p = (Person) selection.getFirstElement();