java - 使用 setText 时内存泄漏

Question

我注意到我的程序中存在内存泄漏。

我已经追查到问题所在了。

Clock.setText("" + h + ":" + df.format(m) + ":" + df.format(s));

我用谷歌搜索了一下，这似乎是一个常见问题，但我还没有找到答案。

有人知道解决办法吗？

完整代码如下:

package CodeBits;

import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DecimalFormat;
import java.util.Calendar;
import java.util.GregorianCalendar;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;

public class Countdown {

    private JFrame Timer;
    private JTextField Clock;
    private JLabel label;
    private JLabel label_1;
    static Calendar calendar = new GregorianCalendar();
    int minutes = 90;
    int count = minutes * 60;
    int h;
    int m;
    int s;
    javax.swing.Timer refreshTimer;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            public void run() {
                try {
                    Countdown window = new Countdown();
                    window.Timer.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the application.
     */
    public Countdown() {
        initialize();
    }

    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {
        Timer = new JFrame();
        Timer.getContentPane().setBackground(new Color(173, 216, 230));
        Timer.setBounds(0, 0, 135, 100);
        Timer.setTitle("Aero Software");
        Timer.setIconImage(Toolkit.getDefaultToolkit().getImage("Files/Icon.jpg"));
        Timer.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        GridBagLayout gridBagLayout = new GridBagLayout();
        gridBagLayout.columnWidths = new int[]{0, 0, 0, 0, 0, 0};
        gridBagLayout.rowHeights = new int[]{0, 0, 0, 0, 0, 0, 0, 0};
        gridBagLayout.columnWeights = new double[]{0.0, 0.0, 1.0, 1.0, 0.0, Double.MIN_VALUE};
        gridBagLayout.rowWeights = new double[]{0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, Double.MIN_VALUE};
        Timer.getContentPane().setLayout(gridBagLayout);

        label = new JLabel(" ");
        GridBagConstraints gbc_label = new GridBagConstraints();
        gbc_label.insets = new Insets(0, 0, 5, 5);
        gbc_label.gridx = 0;
        gbc_label.gridy = 1;
        Timer.getContentPane().add(label, gbc_label);

        JLabel lblNewLabel = new JLabel("Countdown Timer");
        GridBagConstraints gbc_lblNewLabel = new GridBagConstraints();
        gbc_lblNewLabel.gridwidth = 4;
        gbc_lblNewLabel.insets = new Insets(0, 0, 5, 0);
        gbc_lblNewLabel.gridx = 1;
        gbc_lblNewLabel.gridy = 1;
        Timer.getContentPane().add(lblNewLabel, gbc_lblNewLabel);

        Clock = new JTextField();
        Clock.setFont(new Font("Arial", Font.BOLD, 22));
        Clock.setHorizontalAlignment(JLabel.CENTER);
        GridBagConstraints gbc_Clock = new GridBagConstraints();
        gbc_Clock.fill = GridBagConstraints.HORIZONTAL;
        gbc_Clock.gridwidth = 3;
        gbc_Clock.insets = new Insets(0, 0, 5, 5);
        gbc_Clock.gridx = 1;
        gbc_Clock.gridy = 2;
        Timer.getContentPane().add(Clock, gbc_Clock);
        Clock.setColumns(10);

        label_1 = new JLabel(" ");
        GridBagConstraints gbc_label_1 = new GridBagConstraints();
        gbc_label_1.insets = new Insets(0, 0, 5, 0);
        gbc_label_1.gridx = 4;
        gbc_label_1.gridy = 2;
        Timer.getContentPane().add(label_1, gbc_label_1);

        // Create countdown timer                       
        ActionListener refreshListener = new ActionListener() {

            // Ensure time is fotmatted as 7:04 not 7:4
            DecimalFormat df = new DecimalFormat("00");
            Calendar countdown = calendar;

            {
                // Zero the time and add the number of minutes to countdown from
                countdown.set(Calendar.HOUR, 0);
                countdown.set(Calendar.MINUTE, 0);
                countdown.set(Calendar.SECOND, 0);
                countdown.set(Calendar.MINUTE, 0);
                countdown.add(Calendar.MINUTE, minutes);
            }

            // Start the timer
            public void actionPerformed(ActionEvent e) {
                h = countdown.get(Calendar.HOUR_OF_DAY);
                m = countdown.get(Calendar.MINUTE);
                s = countdown.get(Calendar.SECOND);
                calendar.add(Calendar.SECOND, -1);
                Clock.setText("" + h + ":" + df.format(m) + ":" + df.format(s));

                count--;
                if (count == 0) {
                    System.out.println("Time is up!");
                    refreshTimer.stop();
                }

            }
        };

        refreshTimer = new javax.swing.Timer(1000, refreshListener);
        refreshTimer.setInitialDelay(0);
        refreshTimer.start();

    }
}

Answer 1

我觉得你的程序没问题。请注意定期 GC 是如何返回到基线的。相比之下，这个 example泄漏主机资源。最多，您可能会考虑使用 StringBuilder或 MessageFormat在您的 setText() 调用中。