// standard message dialogs
MessageDialog.openConfirm(shell, "Confirm", "Please confirm");
MessageDialog.openError(shell, "Error", "Error occured");
MessageDialog.openInformation(shell, "Info", "Info for you");
MessageDialog.openQuestion(shell, "Question", "Really, really?");
MessageDialog.openWarning(shell, "Warning", "I am warning you!");

// customized MessageDialog with configured buttons
MessageDialog dialog = new MessageDialog(shell, "My Title", null,
    "My message", MessageDialog.ERROR, new String[] { "First",
    "Second", "Third" }, 0);
int result = dialog.open();
System.out.println(result);

boolean result = 
    MessageDialog.openConfirm(shell, "Confirm", "Please confirm");

if (result){
 // OK Button selected do something
} else {
 // Cancel Button selected do something
}

package com.vogella.tasks.ui.handlers;

import java.util.ArrayList;
import java.util.List;

import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.MultiStatus;
import org.eclipse.core.runtime.Status;
import org.eclipse.e4.core.di.annotations.Execute;
import org.eclipse.e4.ui.model.application.ui.basic.MWindow;
import org.eclipse.jface.dialogs.ErrorDialog;
import org.eclipse.swt.widgets.Shell;

public class ShowErrorDialogHandler {
    @Execute
    public void execute(final Shell shell, MWindow window) {
        // create exception on purpose to demonstrate ErrorDialog
        try {
            String s = null;
            System.out.println(s.length());
        } catch (NullPointerException e) {
            // build the error message and include the current stack trace
            MultiStatus status = createMultiStatus(e.getLocalizedMessage(), e);
            // show error dialog
            ErrorDialog.openError(shell, "Error", "This is an error", status);
        }
    }

    private static MultiStatus createMultiStatus(String msg, Throwable t) {

        List<Status> childStatuses = new ArrayList<>();
        StackTraceElement[] stackTraces = Thread.currentThread().getStackTrace();

        for (StackTraceElement stackTrace: stackTraces) {
            Status status = new Status(IStatus.ERROR,
                    "com.vogella.tasks.ui", stackTrace.toString());
            childStatuses.add(status);
        }

        MultiStatus ms = new MultiStatus("com.vogella.tasks.ui",
                IStatus.ERROR, childStatuses.toArray(new Status[] {}),
                t.toString(), t);
        return ms;
    }
}

package com.vogella.plugin.dialogs.custom;

import org.eclipse.jface.dialogs.Dialog;
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Shell;

public class MyDialog extends Dialog {

    public MyDialog(Shell parentShell) {
        super(parentShell);
    }

    @Override
    protected Control createDialogArea(Composite parent) {
        Composite container = (Composite) super.createDialogArea(parent);
        Button button = new Button(container, SWT.PUSH);
        button.setLayoutData(new GridData(SWT.BEGINNING, SWT.CENTER, false,
                false));
        button.setText("Press me");
        button.addSelectionListener(new SelectionAdapter() {
            @Override
            public void widgetSelected(SelectionEvent e) {
                System.out.println("Pressed");
            }
        });

        return container;
    }

    // overriding this methods allows you to set the
    // title of the custom dialog
    @Override
    protected void configureShell(Shell newShell) {
        super.configureShell(newShell);
        newShell.setText("Selection dialog");
    }

    @Override
    protected Point getInitialSize() {
        return new Point(450, 300);
    }

}

package com.vogella.plugin.dialogs.custom;

import org.eclipse.jface.dialogs.IMessageProvider;
import org.eclipse.jface.dialogs.TitleAreaDialog;
import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Text;

public class MyTitleAreaDialog extends TitleAreaDialog {

    private Text txtFirstName;
    private Text lastNameText;

    private String firstName;
    private String lastName;

    public MyTitleAreaDialog(Shell parentShell) {
        super(parentShell);
    }

    @Override
    public void create() {
        super.create();
        setTitle("This is my first custom dialog");
        setMessage("This is a TitleAreaDialog", IMessageProvider.INFORMATION);
    }

    @Override
    protected Control createDialogArea(Composite parent) {
        Composite area = (Composite) super.createDialogArea(parent);
        Composite container = new Composite(area, SWT.NONE);
        container.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
        GridLayout layout = new GridLayout(2, false);
        container.setLayout(layout);

        createFirstName(container);
        createLastName(container);

        return area;
    }

    private void createFirstName(Composite container) {
        Label lbtFirstName = new Label(container, SWT.NONE);
        lbtFirstName.setText("First Name");

        GridData dataFirstName = new GridData();
        dataFirstName.grabExcessHorizontalSpace = true;
        dataFirstName.horizontalAlignment = GridData.FILL;

        txtFirstName = new Text(container, SWT.BORDER);
        txtFirstName.setLayoutData(dataFirstName);
    }
    
    private void createLastName(Composite container) {
        Label lbtLastName = new Label(container, SWT.NONE);
        lbtLastName.setText("Last Name");
        
        GridData dataLastName = new GridData();
        dataLastName.grabExcessHorizontalSpace = true;
        dataLastName.horizontalAlignment = GridData.FILL;
        lastNameText = new Text(container, SWT.BORDER);
        lastNameText.setLayoutData(dataLastName);
    }



    @Override
    protected boolean isResizable() {
        return true;
    }

    // save content of the Text fields because they get disposed
    // as soon as the Dialog closes
    private void saveInput() {
        firstName = txtFirstName.getText();
        lastName = lastNameText.getText();

    }

    @Override
    protected void okPressed() {
        saveInput();
        super.okPressed();
    }

    public String getFirstName() {
        return firstName;
    }

    public String getLastName() {
        return lastName;
    }
}

// more imports
import org.eclipse.jface.window.Window;
import org.eclipse.swt.widgets.Shell;


var dialog = new MyTitleAreaDialog(shell);
// just to demonstrate also how to set the title background color
dialog.setTitleAreaColor(Display.getDefault().getSystemColor(SWT.COLOR_DARK_GRAY).getRGB());

// now open the dialog
dialog.create();
if (dialog.open() == Window.OK) {
    System.out.println(dialog.getFirstName());
    System.out.println(dialog.getLastName());
}

package com.vogella.tasks.ui.handlers;

import org.eclipse.jface.dialogs.Dialog;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Shell;

public class MyNonModularDialog extends Dialog {

    public MyNonModularDialog(Shell parentShell) {
        super(parentShell);
        setShellStyle(SWT.CLOSE | SWT.MODELESS | SWT.BORDER | SWT.TITLE);
        setBlockOnOpen(false);
    }

    @Override
    protected Control createDialogArea(Composite parent) {
        Composite container = (Composite) super.createDialogArea(parent);
        Button button = new Button(container, SWT.PUSH);
        button.setLayoutData(new GridData(SWT.BEGINNING, SWT.CENTER, false, false));
        button.setText("Press");
        return container;
    }

    @Override
    protected Point getInitialSize() {
        return new Point(450, 300);
    }
}