什么是未初始化的引用变量，它不为null

Question

In java, local reference variables do not have a default value of null before they are initialized. What exactly is the difference between a variable with a value of null, and a variable with no value?

Answer 1

An uninitialized reference doesn't have no value, it has an undefined value (and the compiler prevents you from using them, IIRC). A reference initialized to null will result in a equality comparison with null always evaluating to true .

Answer 2

In a less-restrictive language a variable that has not been somehow initialized can contain random data.

In Java an uninitialized variable cannot be referenced. This is enforced by both the compiler and the bytecode verifier.