MemoryLabel.java

package games.strategy.triplea.ui;

import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.lang.ref.WeakReference;
import java.text.DecimalFormat;

import javax.swing.JLabel;
import javax.swing.JPopupMenu;
import javax.swing.SwingUtilities;

import games.strategy.ui.SwingAction;
import games.strategy.util.ThreadUtil;

public class MemoryLabel extends JLabel {
  private static final long serialVersionUID = -6011470050936617333L;

  public MemoryLabel() {
    update();
    addMouseListener(new MouseAdapter() {
      @Override
      public void mouseReleased(final MouseEvent e) {
        if (e.isPopupTrigger()) {
          gc(e);
        }
      }

      @Override
      public void mousePressed(final MouseEvent e) {
        if (e.isPopupTrigger()) {
          gc(e);
        }
      }
    });
    final Thread t = new Thread(new Updater(this), "Memory Label Updater");
    t.start();
  }

  protected void gc(final MouseEvent e) {
    final JPopupMenu menu = new JPopupMenu();
    menu.add(SwingAction.of("Garbage Collect", event -> {
      System.gc();
      System.runFinalization();
      System.gc();
      System.runFinalization();
      System.gc();
    }));
    menu.show(this, e.getX(), e.getY());
  }

  public void update() {
    final long free = Runtime.getRuntime().freeMemory();
    final long total = Runtime.getRuntime().totalMemory();
    final long used = total - free;
    final DecimalFormat format = new DecimalFormat("###.##");
    setText(format.format(used / 1000000.0) + "/" + format.format(total / 1000000.0) + " MB");
  }
}


/**
 * This thread will stop when the label is garbage collected.
 */
class Updater implements Runnable {
  private final WeakReference<MemoryLabel> m_label;

  Updater(final MemoryLabel label) {
    m_label = new WeakReference<>(label);
  }

  @Override
  public void run() {
    while (m_label.get() != null) {
      if (!ThreadUtil.sleep(2000)) {
        return;
      }
      update();
    }
  }

  private void update() {
    SwingUtilities.invokeLater(() -> {
      final MemoryLabel label = m_label.get();
      if (label == null || !label.isVisible()) {
        return;
      }
      label.update();
    });
  }

}