Show/hide JScrollPane scrollbar

 Set using setHorizontalScrollBarPolicy, setVerticalScrollBarPolicy

package test.swing;

import javax.swing.*;
import javax.swing.table.DefaultTableModel;
import java.awt.*;

// JScrollPane scrollbar show / hide
public class MainTest {
    public static void main(String[] args) {
        MainUI mainUI = new MainUI();
        mainUI.setVisible(true);
    }
}

class MainUI extends JFrame {
    JScrollPane scrollPane1 = null;
    JScrollPane scrollPane2 = null;
    JScrollPane scrollPane3 = null;
    JTable table1 = null;
    JTable table2 = null;
    JTable table3 = null;
    DefaultTableModel tableModel = null;

    MainUI() {
        setPreferredSize(new Dimension(400, 600));
        setLayout(new GridLayout(3, 1));

        System.out.println("JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED = " + JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        System.out.println("JScrollPane.HORIZONTAL_SCROLLBAR_NEVER = " + JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
        System.out.println("JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS = " + JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);

        System.out.println("JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED = " + JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
        System.out.println("JScrollPane.VERTICAL_SCROLLBAR_NEVER = " + JScrollPane.VERTICAL_SCROLLBAR_NEVER);
        System.out.println("JScrollPane.VERTICAL_SCROLLBAR_ALWAYS = " + JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

        table1 = new JTable();
        tableModel = (DefaultTableModel) table1.getModel();
        tableModel.addColumn("Column");
        tableModel.addRow(new Object[]{"SCROLLBAR_AS_NEEDED"});
        scrollPane1 = new JScrollPane(table1);
        add(scrollPane1);

        System.out.println("default h policy = " + scrollPane1.getHorizontalScrollBarPolicy() + ", v policy = " + scrollPane1.getVerticalScrollBarPolicy());

        table2 = new JTable();
        tableModel = (DefaultTableModel) table2.getModel();
        tableModel.addColumn("Column");
        tableModel.addRow(new Object[]{"HORIZONTAL_SCROLLBAR_NEVER"});
        tableModel.addRow(new Object[]{"VERTICAL_SCROLLBAR_ALWAYS"});
        scrollPane2 = new JScrollPane(table2);
        scrollPane2.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
        scrollPane2.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
        add(scrollPane2);

        table3 = new JTable();
        tableModel = (DefaultTableModel) table3.getModel();
        tableModel.addColumn("Column");
        tableModel.addRow(new Object[]{"HORIZONTAL_SCROLLBAR_ALWAYS"});
        tableModel.addRow(new Object[]{"VERTICAL_SCROLLBAR_NEVER"});
        scrollPane3 = new JScrollPane(table3);
        scrollPane3.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
        scrollPane3.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_NEVER);
        add(scrollPane3);

        pack();
    }
}

Run

JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED = 30
JScrollPane.HORIZONTAL_SCROLLBAR_NEVER = 31
JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS = 32
JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED = 20
JScrollPane.VERTICAL_SCROLLBAR_NEVER = 21
JScrollPane.VERTICAL_SCROLLBAR_ALWAYS = 22
default h policy = 30, v policy = 20