Fundamentals - SCJP Sun Certified Programmer for Java Platform SE6 - page 38

The argument last is copied into the parameter lastName . The argument first is
copied into the parameter firstName . What gets copied? Well, because last and first are
references, they contain memory addresses, and that is what gets copied. The result is that
lastName points to the same String object as last , which in this example is “Einstein” .
Similarly, firstName points to “Albert” , as shown in Figure 1.11. The objects did not get
copied! There is still only one String object with the value “Einstein” in memory and only
one String object with the value “Albert” in memory.

FIGURE 1.11 The arguments from main are copied into the parameters of findByName .

“Albert”

first firstName

“Einstein”

last lastName

The memory of the
call stack for main

Heap The memory of the

call stack for findByName

Because String objects are immutable, the parameters lastName and firstName cannot
change the objects “Albert” or “Einstein” . Setting the parameters equals to “Jane” and “Doe”

has no effect on first and last , as Figure 1.12 shows. Therefore, the output of that code is

Albert Einstein

FIGURE 1.12 String objects are immutable, so findByName cannot change
first and last .

“Albert”

first firstName

“Einstein”

last lastName

“Jane”

“Doe”

The memory of the
call stack for main

Heap The memory of the

call stack for findByName