Java Casting查询异常和错误

Question

在Java中，什么时候会出现不兼容的类型编译错误，什么时候会出现ClassCastException？

Answer 1

ClassCastException API Specifications clearly says:

Thrown to indicate that the code has attempted to cast an object to a subclass of which it is not an instance.

ClassCastException occurs at runtime because compiler believes that the cast may be a valid one.

Eg:

// The below line will compile but ClassCastException will be raised at runtime
Integer i = (Integer) new Object();

Incompatible type error can easily be resolved by the compiler at compile time itself. It simply looks if the class to which you are trying to cast a specific object falls in the same hierarchy.

Eg:

 String str = "abc"; <br>Integer number = (Integer) str;  
// Compile Error :  Integer and String are not in the same hierarchy