Efficiency of passing in java

Question

Let me see if I understand this. Due to Java's "pass-by-the-value-of-the-reference” nature it is much less costly to pass around an array or large collection of objects (say bitmaps) than it could be... Because you're actually passing a high level reference variable... How far off am I?

Answer 1

"pass-by-the-value-of-the-reference" has it summed up, where the value of the reference [type] is an internal opaque value:

The reference type of the Java virtual machine is cleverly named reference. Values of type reference come in three flavors: the class type, the interface type, and the array type. All three types have values that are references to dynamically created objects.

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The basic unit of size for data values in the Java virtual machine is the word--a fixed size chosen by the designer of each Java virtual machine implementation. The word size must be large enough to hold a value of type byte, short, int, char, float, returnAddress, or reference.

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Notes:

1. Android-Dalvik is not Java-JVM. However, for sake of discussion it takes "equivalent stack space" to pass a reference value and an integer value or utilize a local variable of the same.

2. It's not all about the size. Where possible, passing and using a long is better than a Long, even though the reference value might actually be "smaller".

   Trivially, there is no indirect lookup or boxing/unboxing and associated object required for the long value. (Examples of additional memory locality benefits is better in .NET which supports larger "primitive/struct" values and doesn't need to box/unbox.)

3. The phrase "actually passing a high level reference variable" is wrong because variables are not passed in Java. Only values are passed as arguments: for reference-typed expressions, including simple variable expressions, the reference value is passed.