In this illustration, the header of the column labeled "Long Last Name" overlaps into the adjacent column's space.

overlapping.css

.column-header.left-header > .label {
    -fx-alignment: baseline-left;
}

.column-header.overlap-header > .label {
    -fx-alignment: baseline-right;
    -fx-padding: 0 3 0 0;
}

Code snippet implementing the overlap effect

TableColumn<Person, String> lastNameCol = new TableColumn<>();
lastNameCol.setMinWidth(80);
lastNameCol.setCellValueFactory(
        new PropertyValueFactory<>("lastName"));
lastNameCol.getStyleClass().add("overlap-header");

Label headerLabel = new Label("Long Last Name");
headerLabel.setMinWidth(Control.USE_PREF_SIZE);
lastNameCol.setGraphic(headerLabel);

To achieve this workaround:

1. Use CSS to adjust alignment properties.
2. Utilize a label graphic for the overlapping effect.

By providing a label graphic, you can customize the minimum width to prevent truncation if the header text is too lengthy.

Executable code example

import javafx.application.Application;
import javafx.beans.property.SimpleStringProperty;
import javafx.collections.*;
import javafx.geometry.Insets;
import javafx.scene.*;
import javafx.scene.control.*;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.layout.VBox;
import javafx.scene.text.Font;
import javafx.stage.Stage;

public class TableViewOverlapHeader extends Application {

    private TableView<Person> table = new TableView<>();
    private final ObservableList<Person> data =
        FXCollections.observableArrayList(
            new Person("Jacob", "Smith", "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="0e646f6d616c207d63677a664e6b766f637e626b206d6163">[email protected]</a>"),
            new Person("Isabella", "Johnson", "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="244d574546414848450a4e4b4c4a574b4a64415c45495448410a474b49">[email protected]</a>"),
            new Person("Ethan", "Williams", "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="7a1f0e121b14540d131616131b17093a1f021b170a161f54191517">[email protected]</a>"),
            new Person("Emma", "Jones", "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="0b6e66666a256164656e784b6e736a667b676e25686466">[email protected]</a>"),
            new Person("Michael", "Brown", "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="d4b9bdb7bcb5b1b8fab6a6bba3ba94b1acb5b9a4b8b1fab7bbb9">[email protected]</a>")
        );

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage stage) {
        Scene scene = new Scene(new Group());
        stage.setTitle("Table View Sample");

        table.setPrefHeight(200);

        final Label label = new Label("Address Book");
        label.setFont(new Font("Arial", 20));

        TableColumn<Person, String> firstNameCol = new TableColumn<>("First Name");
        firstNameCol.setMinWidth(100);
        firstNameCol.setCellValueFactory(
                new PropertyValueFactory<>("firstName"));
        firstNameCol.getStyleClass().add("left-header");

        TableColumn<Person, String> lastNameCol = new TableColumn<>();
        lastNameCol.setMinWidth(80);
        lastNameCol.setCellValueFactory(
                new PropertyValueFactory<>("lastName"));
        lastNameCol.getStyleClass().add("overlap-header");

        Label headerLabel = new Label("Long Last Name");
        headerLabel.setMinWidth(Control.USE_PREF_SIZE);
        lastNameCol.setGraphic(headerLabel);

        TableColumn<Person, String> emailCol = new TableColumn<>("Email");
        emailCol.setMinWidth(100);
        emailCol.setCellValueFactory(
                new PropertyValueFactory<>("email"));

        table.setItems(data);
        table.getColumns().addAll(firstNameCol, lastNameCol, emailCol);

        final VBox vbox = new VBox();
        vbox.setSpacing(5);
        vbox.setPadding(new Insets(10));
        vbox.getChildren().addAll(label, table);

        ((Group) scene.getRoot()).getChildren().addAll(vbox);

        scene.getStylesheets().add(getClass().getResource("overlap.css").toExternalForm());

        stage.setScene(scene);
        stage.show();
    }

    public static class Person {
        private final SimpleStringProperty firstName;
        private final SimpleStringProperty lastName;
        private final SimpleStringProperty email;

        private Person(String fName, String lName, String email) {
            this.firstName = new SimpleStringProperty(fName);
            this.lastName = new SimpleStringProperty(lName);
            this.email = new SimpleStringProperty(email);
        }

        public String getFirstName() {
            return firstName.get();
        }

        public void setFirstName(String fName) {
            firstName.set(fName);
        }

        public String getLastName() {
            return lastName.get();
        }

        public void setLastName(String fName) {
            lastName.set(fName);
        }

        public String getEmail() {
            return email.get();
        }

        public void setEmail(String fName) {
            email.set(fName);
        }
   }
}