Profiling the SnowStorm Application in Java

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Profiling the SnowStorm Application
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delete snowflake from snowflakes;
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Now start the profiler by clicking the Profile button as before, but this time choose Memory Profiling in the Profile dialogThe Profile dialog offers you the option of increasing or decreasing the amount of profiling information to be gatheredAs before, collecting more information causes more overhead, so the usual approach is to accept the default for the first run and add more later, if you need toTo start gathering information, click the Run buttonWhen the application starts running, the profiling pane appears, and you can click the Live Results button to see the objects that are being created, as shown in Figure 4-28 When looking for memory leaks, it is important to realize that a lot of garbage may remain uncollected until the JVM needs to reclaim space Just because there is apparently a large number of a particular type of object shown in the memory profile does not necessarily mean that those objects are not being collected when they should If you suspect a leak, the first thing to do is to force a full garbage collectionYou can do this by clicking the button that looks like a dustbin on the profiling pane If you do this, you ll find that there is clearly a memory leak For one thing, the total amount of used memory is increasing and does not fall very far after garbage collectionThis value can be seen in the Basic Telemetry section at the bottom of the profiling pane and also in Figure 4-29 If you look at the objects that are taking up most space, you ll see that they all belong to the JavaFX runtime None of them is obviously anything to do with code in the SnowStorm application Just to make sure, let s see what is happening to objects that we might have createdTo do this, type the value javafxsceneshape in the Filter field below the memory profiling results and press EnterThis narrows down the results only to
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Figure 4-27
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A CPU profile snapshot
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4 A Simple JavaFX Application
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Figure 4-28
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Using the memory profiler
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Figure 4-29
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Basic Telemetry in the NetBeans profiler
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objects whose classnames match the filter stringYou will immediately see that lots of circle objects have been allocated and, most significantly, if you force a garbage collection, none of them are released the count of active instances continues to riseThis points pretty directly to the bug that we deliberately introduced If you fix the bug and rerun the profiler, you ll see that the memory leak is gone As with the CPU profiler, the memory profiler enables you to take and save snapshots for comparison or later analysis
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Source Code for the SnowStorm Application
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For reference, here is the complete source code for the SnowStorm application
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The SnowStorm Application
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package javafxexample; import import import import javalangSystem; javautilRandom; javafxanimationKeyFrame; javafxanimationTimeline;
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Source Code for the SnowStorm Application
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import import import import import import import import
javafxsceneimageImage; javafxsceneimageImageView; javafxscenepaintColor; javafxsceneScene; javafxsceneshapeCircle; javafxscenetextFont; javafxscenetextText; javafxstageStage;
// Static user interface setup // The scene that contains the snow var scene:Scene; Stage { title: "JavaFX Snow Storm" resizable: false scene: scene = Scene { content: [ ImageView { image: Image { url: "{__DIR__}SnowScenepng" }; }, Text { x: 25 y: bind sceneheight - 10 font: Font { size: 20 } content: bind "Snowflakes: {sizeof snowflakes}" } ] } } // Animation // The snowflakes var snowflakes:Circle[]; // Time interval for new snow def newSnowTime = 500ms; // Number of snowflakes per row def snowflakesPerLine = 5; // Random number generator
4 A Simple JavaFX Application
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def rand = new Random(SystemcurrentTimeMillis()); // Periodically add snow def addSnowTimeline = Timeline { repeatCount: TimelineINDEFINITE keyFrames: [ KeyFrame { time: newSnowTime action: addNewSnow } ] }; addSnowTimelineplay(); // Adds new snow to the scene function addNewSnow() { var sectionWidth = (scenewidth + snowflakesPerLine - 1) / snowflakesPerLine; for (i in [0<snowflakesPerLine]) { var x = sectionWidth * i + randnextInt(sectionWidth); var snowflake = Circle { centerX: x centerY: 0 radius: 2 cache: true fill: ColorWHITE } insert snowflake into scenecontent; insert snowflake into snowflakes; } } // Animating the snowflakes // Time interval for moving the snow def moveSnowTime = 100ms; // How far the snow falls in each frame def snowFallDistance = 4; // Drift distance def snowDriftDistance = 4; // Periodically move snow def moveSnowTimeline = Timeline { repeatCount: TimelineINDEFINITE keyFrames: [ KeyFrame {