10.3 实例应用 · Java 开源项目中文文档

## 10.3 实例应用 ### 10.3.1 概述实例MemoryUsageDemo.java文档可以从下面的链接中获得： [http://www.object-refinery.com/jfreechart/premium/index.html](http://www.object-refinery.com/jfreechart/premium/index.html) 页面需要输入购买JFreeChart开发指南时需要的用户名和密码。 ### 10.3.2 创建一个dataset 创建的实例代码数据源，包含了一个单一的时序集合，集合内有两个TimeSeries对象（一个是计算总内存，另一个是计算剩余内存）。代码如下： ``` this.total = new TimeSeries("Total", Millisecond.class); this.total.setMaximumItemAge(30000); this.free = new TimeSeries("Free", Millisecond.class); this.free.setMaximumItemAge(30000); TimeSeriesCollection dataset = new TimeSeriesCollection(); dataset.addSeries(this.total); dataset.addSeries(this.free); ``` 每个时间系列的maximumItemAge属性设置为30000毫秒（30秒）。因此任何时候添加到新系列的新数据，都是30秒前记录的老数据。 ### 10.3.3 创建一个图表图表的创建（定制）都遵循所有图表创建的标准模式。创建动态图也是一样，没有任何特殊的步骤。除了我们将autoRange属性设置为true之外。同时，这也有利于维护图表使用的数据源的引用。 ### 10.3.4 更新一个dataset 在本实例演示中，通过向两个时序图添加的数据来更新数据源，该数据的添加有一个独立的线程Timer管理。代码如下： ``` class DataGenerator extends Timer implements ActionListener { DataGenerator(int i) { super(i, null); addActionListener(this); } public void actionPerformed(ActionEvent actionevent) { long l = Runtime.getRuntime().freeMemory(); long l_0_ = Runtime.getRuntime().totalMemory(); MemoryUsageDemo.this.addTotalObservation((double) l_0_); MemoryUsageDemo.this.addFreeObservation((double) l); } } ``` 注意JFreeChart在画图表和数据源更新代码之间没有使用线程同步，因此是不安全的。另一点需要注意的是，曾做过一个关于JFreeChart内存泄露问题的测试，将JFreeChart的实例在一个机器上连续运行6天。随着图表的不断更新，我们就可以看到垃圾收集器所产生的影响。六天之后，发现总内存的使用量保持不变。当JFreChart产生并丢弃的临时对象（垃圾对象）时，剩余可用内存减少了。增加的使用内存量是垃圾收集器工作时所使用的。 ### 10.3.5 全部代码下面是全部的实例代码： ``` /* MemoryUsageDemo - Decompiled by JODE * Visit http://jode.sourceforge.net/ */ package demo; import java.awt.BasicStroke; import java.awt.BorderLayout; import java.awt.Color; import java.awt.Font; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import javax.swing.BorderFactory; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.Timer; import org.jfree.chart.ChartPanel; import org.jfree.chart.JFreeChart; import org.jfree.chart.axis.DateAxis; import org.jfree.chart.axis.NumberAxis; import org.jfree.chart.plot.XYPlot; import org.jfree.chart.renderer.xy.XYLineAndShapeRenderer; import org.jfree.data.time.Millisecond; import org.jfree.data.time.TimeSeries; import org.jfree.data.time.TimeSeriesCollection; import org.jfree.ui.RectangleInsets; public class MemoryUsageDemo extends JPanel { private static final long serialVersionUID = 6776712838359498649L; private TimeSeries total; private TimeSeries free; /* synthetic */ static Class class$org$jfree$data$time$Millisecond; class DataGenerator extends Timer implements ActionListener { private static final long serialVersionUID = 1L; DataGenerator(int i) { super(i, null); addActionListener(this); } public void actionPerformed(ActionEvent actionevent) { long l = Runtime.getRuntime().freeMemory(); long l_0_ = Runtime.getRuntime().totalMemory(); MemoryUsageDemo.this.addTotalObservation((double) l_0_); MemoryUsageDemo.this.addFreeObservation((double) l); } } public MemoryUsageDemo(int i) { super(new BorderLayout()); total = new TimeSeries( "Total Memory", (class$org$jfree$data$time$Millisecond == null ? (class$org$jfree$data$time$Millisecond = class$("org.jfree.data.time.Millisecond")) : class$org$jfree$data$time$Millisecond)); total.setMaximumItemAge((long) i); free = new TimeSeries( "Free Memory", (class$org$jfree$data$time$Millisecond == null ? (class$org$jfree$data$time$Millisecond = class$("org.jfree.data.time.Millisecond")) : class$org$jfree$data$time$Millisecond)); free.setMaximumItemAge((long) i); TimeSeriesCollection timeseriescollection = new TimeSeriesCollection(); timeseriescollection.addSeries(total); timeseriescollection.addSeries(free); DateAxis dateaxis = new DateAxis("Time"); NumberAxis numberaxis = new NumberAxis("Memory"); dateaxis.setTickLabelFont(new Font("SansSerif", 0, 12)); numberaxis.setTickLabelFont(new Font("SansSerif", 0, 12)); dateaxis.setLabelFont(new Font("SansSerif", 0, 14)); numberaxis.setLabelFont(new Font("SansSerif", 0, 14)); XYLineAndShapeRenderer xylineandshaperenderer = new XYLineAndShapeRenderer( true, false); xylineandshaperenderer.setSeriesPaint(0, Color.red); xylineandshaperenderer.setSeriesPaint(1, Color.green); xylineandshaperenderer.setSeriesStroke(0, new BasicStroke(3.0F, 0, 2)); xylineandshaperenderer.setSeriesStroke(1, new BasicStroke(3.0F, 0, 2)); XYPlot xyplot = new XYPlot(timeseriescollection, dateaxis, numberaxis, xylineandshaperenderer); xyplot.setBackgroundPaint(Color.lightGray); xyplot.setDomainGridlinePaint(Color.white); xyplot.setRangeGridlinePaint(Color.white); xyplot.setAxisOffset(new RectangleInsets(5.0, 5.0, 5.0, 5.0)); dateaxis.setAutoRange(true); dateaxis.setLowerMargin(0.0); dateaxis.setUpperMargin(0.0); dateaxis.setTickLabelsVisible(true); numberaxis.setStandardTickUnits(NumberAxis.createIntegerTickUnits()); JFreeChart jfreechart = new JFreeChart("JVM Memory Usage", new Font( "SansSerif", 1, 24), xyplot, true); jfreechart.setBackgroundPaint(Color.white); ChartPanel chartpanel = new ChartPanel(jfreechart, true); chartpanel.setBorder(BorderFactory.createCompoundBorder(BorderFactory .createEmptyBorder(4, 4, 4, 4), BorderFactory .createLineBorder(Color.black))); add(chartpanel); } private void addTotalObservation(double d) { total.add(new Millisecond(), d); } private void addFreeObservation(double d) { free.add(new Millisecond(), d); } public static void main(String[] strings) { JFrame jframe = new JFrame("Memory Usage Demo"); MemoryUsageDemo memoryusagedemo = new MemoryUsageDemo(30000); jframe.getContentPane().add(memoryusagedemo, "Center"); jframe.setBounds(200, 120, 600, 280); jframe.setVisible(true); memoryusagedemo.new DataGenerator(100).start(); jframe.addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent windowevent) { System.exit(0); } }); } /* synthetic */static Class class$(String string) { Class var_class; try { var_class = Class.forName(string); } catch (ClassNotFoundException classnotfoundexception) { throw new NoClassDefFoundError(classnotfoundexception.getMessage()); } return var_class; } } ```