java – 为什么不能将Object []转换为String []
发布时间:2020-12-14 05:32:10 所属栏目:Java 来源:网络整理
导读:没有错误 Object[] a = new String[]{"12","34","56"};String[] b = (String[]) a; 没有错误 Object a = new String[]{"12","56"}; String[] b = (String[]) a; 运行时错误:ClassCastException Object[] a = new Object[3];a[0] = "12";a[1] = "34";a[2] =
>没有错误
Object[] a = new String[]{"12","34","56"}; String[] b = (String[]) a; >没有错误 Object a = new String[]{"12","56"}; String[] b = (String[]) a; >运行时错误:ClassCastException Object[] a = new Object[3]; a[0] = "12"; a[1] = "34"; a[2] = "56"; String[] b = (String[]) a; >运行时错误:ClassCastException Object[] a = {"12","56"}; String[] b = (String[]) a; 当然,如果一个Object []变量被创建为一个String [],我们可以将其转换回String []. 我的问题是为什么当Object []创建为Object []但它的所有成员都是String时,我们不能将Object []转换为String []是因为安全原因还是对实现这个没有帮助? 解决方法
这里有两个原因可以想到.
首先,如果您更改原始数组,则转换的数组可能无效.例如 Object[] a = {"12","56"}; String[] b = (String[]) a; // pretend this is legal. a and b now point to the same array a[0] = new Object(); // clearly ok String x = b[0]; // No longer a string! Bad things will happen! 其次,您所选择的示例非常简单,但如果您有一个非常大的Object []数组,并且编译器不清楚填充它,那么它无法验证数组的每个元素都满足该转换. Object[] a = new Object[10000]; // lots of weird and whacky code to fill the array with strings String[] b= (String[]) a; // valid or no? The best-defined answer is to say no. (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |