将超类型的数组转换为子类型 [英] Casting arrays of a supertype to a subtype

问题描述

在Java中导致运行时异常而不是编译时错误的原因是否存在？

Is there a particular reason why this results in runtime exception instead of compile-time error in Java?

Object[] objects = new Object[10];
String[] strings = (String[])objects;

推荐答案

由于以下原因，必须在运行时进行检查：这种情况：

The check has to be done at run time because of this case:

public class Test {
  public static void main(String[] args){
    String[] stringsBase = {"aaa", "bbb", "ccc"};
    Object[] objects = stringsBase;
    String[] strings = (String[])objects;
    System.out.println(strings[1]);
  }
}

这是一个有效的工作程序。如果不进行流分析，编译器将不知道对象是引用创建为Object []的数组，还是引用为String []的数组。

This is a valid, working program. Without doing flow analysis, the compiler does not know whether objects references an array that was created as Object[], or one that was created as, in this case, a String[].

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