The benefits of a Java local variable plus final modification

In general, there are several uses for the following:
1, for the loop, the use of local variables to save the loop several times, and final modification, rather than directly with GetCount (), GetSize (), lenght, etc.
2, when you need to access an object in the collection, use local variables to refer to, and final decoration, rather than direct reference
3, need to access an external object, using local variables to reference, and final decoration, rather than direct reference
4. Other circumstances

The benefits of personal understanding are:
1. Accessing local variables is faster than accessing member variables
2, access to local variables than each call method to get objects faster
3. Use final decoration to avoid variable assignment (reference assignment)
4. When using final adornments, the JVM does not have to keep track of whether the reference has been changed.

Here are some insights to see on the Web:

Accessing a local variable is faster than accessing a field.  It ' s best to keep field accesses out of performance-critical inner loops when possible.  (Profile a course, to the if it matters.) In theory the JVM could "inline" the field to a local variable automatically under the right conditions, but don ' t count O n it.

A final local variable isn't any different the from the normal local variable at runtime. The "final" keyword on a local variable expresses a constraint on the source code (which is assigned to once) which the Compiler can easily check.

Final *fields* do allow additional optimizations, and static final fields with primitive values (as in) public static FINA l INT my_constant = 3 ") are treated as Compile-time constants and inlined.