新類對象創建Java java.lang.StackOverflowError：可能的遞歸？

Question

從類創建對象時出現錯誤。

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(); 
}... 

程序迭代，在Gameworld之前打印並進入下面的行然後重複。

gw = new GameWorld(); 

遊戲世界級

public class GameWorld extends Game { 

private int gameWidth; 
private int gameHeight; 

public GameWorld(){ 

    //init(); 

    System.out.println("after inititalization"); 
}... 

收到以下錯誤在Eclipse上運行。

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) 

我在做什麼錯？爲什麼它循環這麼多？

Answer 1

由於無限循環創建Game對象，您會得到java.lang.StackOverflowError異常。這是調用的是落在循環，並導致StackOverflowError序列：

new Game() => new GameWorld() => new Game() .... 

在Java中，一個子類總是調用它的父類的構造隱含或致電super()明確。因此，GameWorld構造函數將調用Game默認構造函數，然後再次調用GameWorld構造函數，並且它將永遠持續下去。

Answer 2

GameWorld擴展了遊戲。

因此，每次調用小孩ctor時，都會調用它的超類ctor。

案件解決。

您對新GameWorld的調用會隱式調用新遊戲，因爲編譯器會將調用插入super（）到您的構造函數中。

除此之外：A延伸B表示A是B.

但遊戲世界是不是遊戲！所以這從建模角度來看也是錯誤的！