Post on 21-May-2020
Trisha Gee (@trisha_gee)
Developer & Technical Advocate, JetBrains
Refactoring to Java 8
Why Java 8?
It’s Faster
•Performance Improvements in Common Data Structures
•Fork/Join Speed Improvements
•Changes to Support Concurrency
•…and more
http://bit.ly/refJ8
Easy to Parallelize
Fewer Lines of Code
New Solutions to Problems
Minimizes Errors
Safety Check
Test Coverage
Performance Tests
Decide on the Goals
Limit the Scope
Refactoring!
Lambda Expressions
Automatic Refactoring
•Predicate
•Comparator
•Runnable
•etc…
Abstract classes
Advanced Search
Collections & Streams API
Automatic Refactoring
•For loop to collect
•For loop to forEach
•…with and without Streams
Manual Refactoring
Optional
But what about performance?
Lambdas
0
20
40
60
80
100
120
140
160
180O
ps/
ms
Anonymous Inner Classes vs Lambdas
Anonymous Inner Class Lambda
http://www.oracle.com/technetwork/java/jvmls2013kuksen-2014088.pdf
0
2
4
6
8
10
12
14
16
18
20
single thread max threads
nse
c/o
p
Performance of Capture
anonymous(static) anonymous(non-static) lambda
0
50,000
100,000
150,000
200,000
250,000
300,000
350,000
400,000
450,000
500,000
Constant message Variable message
Op
s/m
sLogging Performance
Direct call Lambda
Streams vs Iteration
0
1
2
3
4
5
6
7
8
9
Op
s/m
sIterator vs Stream (1000 elements)
for loop forEach()
0
1000
2000
3000
4000
5000
6000
7000
1 10 100 1000
Op
s/m
sIterHelper
original simplified refactored
0
1
2
3
4
5
6
7
8
9
1000 10000 100000
Op
s/m
sIterHelper
original simplified refactored
BasicDAO – map & collect
0
5000
10000
15000
20000
25000
1 10 100 1000
Op
s/m
s
BasicDAO
original simplified refactored
DuplicatedAttributeNames – filter, map & collect
0
200
400
600
800
1000
1200
Op
s/m
sDuplicatedAttributeNames
original refactored
EntityScanner– forEach
0
0.01
0.02
0.03
0.04
0.05
0.06
Op
s/m
sEntityScanner
original refactored
DatastoreImpl – filter & forEach
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Op
s/m
sDatastoreImpl
original refactored
MappingValidator – single stream operation
0
100
200
300
400
500
600
700
800
900
EntityWithOneError EntityWith10Errors EntityWith20Errors
Op
s/m
sMappingValidator
original refactored
QueryImpl – multiple operations
0
500
1000
1500
2000
2500
3000
3500
Op
s/m
sQueryImpl
original simplified refactored
Going parallel
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Serial Parallel
Tim
e Ta
ken
(se
con
ds)
map()
MacBook Surface
0
20
40
60
80
100
120
140
160
Serial Parallel
Tim
e Ta
ken
(m
illis
)findAny()
MacBook Surface
Optional
0
50,000
100,000
150,000
200,000
250,000
300,000
350,000
Value not null Value null
Op
s/m
sCompare Constant Field Value with Null
Null check Optional
0
50,000
100,000
150,000
200,000
250,000
300,000
Value not null Value null
Op
s/m
sCompare Variable Field Value with Null
Null check Optional
Summary
Sometimes new idioms decrease clutter
…but sometimes they don’t
Sometimes the new features improve performance
0
20
40
60
80
100
120
140
160
180O
ps/
ms
Anonymous Inner Classes vs Lambdas
Anonymous Inner Class Lambda
…and sometimes they don’t
0
200
400
600
800
1000
1200
Op
s/m
sDuplicatedAttributeNames
original refactored
Sometimes a new feature makes life easier
…sometimes not so much
Some refactoring can safely be done automatically
…often you need a human brain
Conclusion
Should you migrate your code to Java 8?
It Depends
Always remember what your goal is
And compare results to it
Understand what may impact performance
And if in doubt, measure
Code may magically improve
Or you may expose areas for improvement
Your tools can help you
But you need to apply your brain too