请考虑以下try-with-resources块：
try (Foo foo = getAFoo()) {
}
对于实现java.lang.AutoCloseable的一些类Foo.
如果getAFoo()返回null,那么将在结束大括号上抛出一个空指针异常(由于运行时尝试调用close)？
解决方法
根据
this Oracle blog：
After due consideration the JSR 334 expert group has decided the semantics of the try-with-resources statement on a null resource should be changed as follows: the compiler-generated calls to close a resource will only occur if the resource is non-null.
