关于java数组复制与多态

最新推荐文章于 2024-06-23 15:17:52 发布

Falme

最新推荐文章于 2024-06-23 15:17:52 发布

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分类专栏： java复习文章标签： java

本文链接：https://blog.youkuaiyun.com/qq_22884121/article/details/53022882

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首先有三个类，如下所示

public class Apple {
    
    private String appleName;
    
    private String appleColor;
    
    private String appleProvider;

    public Apple() {
    }

    public void setAppleColor(String appleColor) {
        this.appleColor = appleColor;
    }
    public String getAppleColor() {
        return appleColor;
    }

    public void setAppleName(String appleName) {
        this.appleName = appleName;
    }
    public String getAppleName() {
        return appleName;
    }

    public void setAppleProvider(String appleProvider) {
        this.appleProvider = appleProvider;
    }
    public String getAppleProvider() {
        return appleProvider;
    }
}

public class BlueApple extends Apple {
    public BlueApple() {
        setAppleColor("blue");
    }
    void setBlue(){}
}

public class RedApple extends Apple {
    public RedApple() {
        setAppleColor("red");
    }
    void setRed(){}

}

如果是如下一段代码

RedApple[] redApple = new RedApple[20];

Apple[] apple = redApple;

apple[0] = new BlueApple();

就会报异常，为什么呢？原因是apple数组和redApple 引用同一块内存，储存的是相同的引用。查了半天资料也没查到权威的解释，根据C++的数组，感觉apple和redApple会先指向同一块内存，两个数组共同对这一块内存修改。所以下面的多态赋值就报异常了。