Possible Duplicate:
String and Final
From http://docs.oracle.com/javase/6/docs/api/java/lang/String.html I can read that:
Strings are constant; their values cannot be changed after they are created.
Does this mean that a final String does not really make sense in Java, in the sense that the final attribute is somehow redundant?
The String object is immutable but what it is is actually a reference to a String object which could be changed.
For example:
String someString = "Lala";
You can reassign the value held by this variable (to make it reference a different string):
someString = "asdf";
However, with this:
final String someString = "Lala";
Then the above reassignment would not be possible and would result in a compile-time error.
final refers to the variable, not the object, so yes, it make sense.
e.g.
final String s = "s";
s = "a"; // illegal
It makes sense. The final keyword prevents future assignments to the variable. The following would be an error in java:
final String x = "foo";
x = "bar" // error on this assignment
References are final, Objects are not. You can define a mutable object as final and change state of it. What final ensures is that the reference you are using cannot ever point to another object again.
来源：https://stackoverflow.com/questions/10233309/does-it-make-sense-to-define-a-final-string-in-java