使用setText时内存泄漏

Question

我注意到我的程序中有内存泄漏。

我已将问题追溯到该行。

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

我用谷歌搜索了这个似乎是一个常见的问题，但我还没有找到答案。

有人知道修复吗？

以下是整个代码：

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

你的程序看起来不错。请注意周期性GC如何返回基线。相反，这个example会泄漏主机资源。您最多可以考虑在setText()调用中使用StringBuilder或MessageFormat。

Answer 2

以下是代码略有修改版本的输出。

14145904
13602336
13059104
12515968
12063384
15263600
14758304
14253408
13748576
13197160
12646360
12057192
11552120
15472056
14960064
14448336
13875144
13363416
12851488
12309120
11681480
15661104
15142224
14602560
14063128
13523464
12983832
12444168
11904536
11364648
15325136
14770848
14230296
13690032
..

我发现这里没有内存泄漏。

更改代码

import java.awt.*;
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.*;

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);

        ActionListener memoryListener = new ActionListener() {
            public void actionPerformed(ActionEvent ae) {
                System.out.println(Runtime.getRuntime().freeMemory());
            }
        };
        Timer memTimer = new Timer(1000,memoryListener);
        memTimer.start();

        // 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(10, refreshListener);
        refreshTimer.setInitialDelay(0);
        refreshTimer.start();

    }
}