[英]Java java.lang.StackOverflowError on New Class Object Creation: possible recursion?
从类创建对象时出现错误。
public class Game extends Form {
private GameWorld gw;
private int lives;
private int clock;
public Game() {
// initialize game
init();
System.out.println("before gameworld: ");
gw = new GameWorld();
System.out.println("after gameworld: ");
gw.init();
play();
}...
程序进行迭代,在Gameworld之前打印并转到下面的行,然后重复。
gw = new GameWorld();
游戏世界类
public class GameWorld extends Game {
private int gameWidth;
private int gameHeight;
public GameWorld(){
//init();
System.out.println("after inititalization");
}...
运行时在Eclipse中出现以下错误。
java.lang.StackOverflowError
at com.codename1.ui.plaf.DefaultLookAndFeel.getPreferredSize(DefaultLookAndFeel.java:675)
at com.codename1.ui.plaf.DefaultLookAndFeel.getLabelPreferredSize(DefaultLookAndFeel.java:665)
at com.codename1.ui.Label.calcPreferredSize(Label.java:484)
at com.codename1.ui.Component.preferredSizeImpl(Component.java:1985)
at com.codename1.ui.Component.preferredSize(Component.java:2020)
at com.codename1.ui.Component.getPreferredSize(Component.java:782)
at com.codename1.ui.Component.getPreferredW(Component.java:862)
at com.codename1.ui.layouts.BorderLayout.getPreferredSize(BorderLayout.java:440)
at com.codename1.ui.Container.calcPreferredSize(Container.java:1848)
at com.codename1.ui.Component.preferredSizeImpl(Component.java:1985)
at com.codename1.ui.Component.preferredSize(Component.java:2020)
at com.codename1.ui.Component.getPreferredSize(Component.java:782)
at com.codename1.ui.Component.getPreferredH(Component.java:872)
at com.codename1.ui.layouts.BorderLayout.positionTopBottom(BorderLayout.java:414)
at com.codename1.ui.layouts.BorderLayout.layoutContainer(BorderLayout.java:284)
at com.codename1.ui.Container.doLayout(Container.java:1420)
at com.codename1.ui.Container.layoutContainer(Container.java:1412)
at com.codename1.ui.Container.revalidate(Container.java:1058)
at com.codename1.ui.Toolbar$ToolbarSideMenu.initMenuBar(Toolbar.java:1233)
at com.codename1.ui.Form.setMenuBar(Form.java:3229)
at com.codename1.ui.Form.setToolbar(Form.java:3250)
at com.codename1.ui.Form.initGlobalToolbar(Form.java:218)
at com.codename1.ui.Form.<init>(Form.java:210)
at com.codename1.ui.Form.<init>(Form.java:166)
at com.mycompany.racecar.Game.<init>(Game.java:19)
at com.mycompany.racecar.GameWorld.<init>(GameWorld.java:8)
at com.mycompany.racecar.Game.<init>(Game.java:25)
at com.mycompany.racecar.GameWorld.<init>(GameWorld.java:8)
at com.mycompany.racecar.Game.<init>(Game.java:25)
at com.mycompany.racecar.GameWorld.<init>(GameWorld.java:8)
at com.mycompany.racecar.Game.<init>(Game.java:25)
at com.mycompany.racecar.GameWorld.<init>(GameWorld.java:8)
at com.mycompany.racecar.Game.<init>(Game.java:25)
at com.mycompany.racecar.GameWorld.<init>(GameWorld.java:8)
at com.mycompany.racecar.Game.<init>(Game.java:25)
at com.mycompany.racecar.GameWorld.<init>(GameWorld.java:8)
at com.mycompany.racecar.Game.<init>(Game.java:25)
at com.mycompany.racecar.GameWorld.<init>(GameWorld.java:8)
at com.mycompany.racecar.Game.<init>(Game.java:25)
我究竟做错了什么? 为什么循环这么多?
由于创建Game
对象时出现无限循环,因此会出现java.lang.StackOverflowError
异常。 这是陷入循环并导致StackOverflowError
的调用序列:
new Game() => new GameWorld() => new Game() ....
在Java中,子类始终隐式地或通过显式调用super()
来调用其父构造函数。 因此, GameWorld
构造函数将调用Game
默认构造函数,然后再次调用GameWorld
构造函数,它将永远存在。
GameWorld扩展了游戏。
因此,每次调用子ctor时,都会调用其父类ctor。
案子解决了。
您对new GameWorld的调用会隐式调用new Game,因为编译器会将对super()的调用插入到您的构造函数中。
除此之外:A扩展B意味着A是B。
但是GameWorld不是游戏! 因此,从建模角度来看,这也是错误的!
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