在Java中将大对象作为参数传递是否效率低下？

Question

Let's say for example I have a class A that creates an instance of a fairly big object B. Is passing B as a parameter to a method in a class C inefficient?

That is, does it just pass a reference or does it shift the object's memory around as well?

Thanks.

Answer 1

It just passes a reference. It's important to understand that the value of any expression in Java is never an object. It's only ever a reference or a primitive value.

This isn't just relevant for parameter passing - it's important to understand for return types, arrays, simple assignment etc.

Answer 2

Java can only pass two kinds of values to a method:

• primitive values ( int , char , double , ...) or
• object references

There is no way you can pass a whole object "by value".

This means that you don't need to worry about "how big" your object is that you "pass around".

Answer 3

它效率不高，因为只有对象引用传递给方法。

Answer 4

只要您的调用是本地的（相同的JVM）对象大小无关紧要，但是当您的应用程序使用远程调用（如RMI / Web Service）（跨JVM）时，大型对象能够在很大程度上减慢您的应用程序因为巨大的将被编组/解组的数据量以及每个远程调用所涉及的网络延迟。

Answer 5

As others have said, in Java you only have pass-by-value. These values are only primitives and references. The largest a primitive or reference can be is 8-bytes. IMHO, there is no such thing as a large argument.

Answer 6

没有什么比内存移位...它只是传递实际的参考..而参考词本身代表一些地址..所以没有问题..它的效率比参数传递真正使代码更复杂..可能就是为什么SUN把它添加到java ...

Answer 7

它只是将引用作为值传递。

Answer 8

Java passes references to objects by value . It makes no difference performance-wise whether the object reference being passed to C is big or not.