Simple JProgressBar test showing high CPU usage on MacOS/Aqua L&F.

ProgressBarTest.java

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class ProgressBarTest extends JFrame {
  private final JProgressBar progressBar = new JProgressBar();
  private final JButton button = new JButton("Toggle Progress Bar State");

  public ProgressBarTest() {
    initComponents();
  }

  private void initComponents() {
    button.setText("Toggle Progress Bar State");
    button.addActionListener(new ActionListener() {
      @Override
      public void actionPerformed(ActionEvent e) {
        progressBar.setIndeterminate(!progressBar.isIndeterminate());
      }
    });
    getContentPane().add(progressBar, BorderLayout.NORTH);
    getContentPane().add(button, BorderLayout.SOUTH);

    pack();
  }

  public static void main(String args[]) {
    SwingUtilities.invokeLater(new Runnable() {
      @Override
      public void run() {
        new ProgressBarTest().setVisible(true);
      }
    });
  }
}

We are facing the same problem.
Is this being reported as bug ?

Writing up the bug report now...