109,740
students have developed their Java skills on Exercism.

Students
109,740
Submissions
1,011,473
Mentoring Discussions
12,932

The Java track needs attention ⚠️

Building

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Use your knowledge to build the Java track itself

Create the Java syllabus

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Help create the track syllabus: is a set of concepts and learning exercises put together to teach foundational elements of the programming language.

Next goal: Create a complete syllabus with at least 20 concepts. Find out more.

Usage statistics

17 concepts being taught
Ba
Basics
14,184 learnt
Bo
Booleans
7,735 learnt
Ar
Arrays
3,196 learnt
Fo
For Loops
3,196 learnt
Fo
For-Each Loops
3,196 learnt
Ge
Generic Types
2,025 learnt
Li
Lists
2,025 learnt
Ch
Chars
1,996 learnt
Cl
Classes
1,774 learnt
Co
Conditionals If
4,092 learnt
Co
Constructors
1,358 learnt
In
Interfaces
1,015 learnt
Nu
Numbers
3,017 learnt
St
Strings
5,200 learnt
Te
Ternary Operators
1,614 learnt
Sw
Switch Statements
1,175 learnt
In
Inheritance
1,094 learnt
14 active learning exercises
Started
Attempts
Completions
Mentoring requests
Cook your lasagna Cook your lasagna
22,880
110,315 (avg. 4.8)
14,184 (62.0%)
124 (0.5%)
Annalyn's Infiltration Annalyn's Infiltration
10,077
76,446 (avg. 7.6)
7,735 (76.8%)
82 (0.8%)
Bird Watcher Bird Watcher
3,658
48,466 (avg. 13.2)
3,196 (87.4%)
41 (1.1%)
Karl's Languages Karl's Languages
2,172
9,789 (avg. 4.5)
2,025 (93.2%)
16 (0.7%)
Squeaky Clean Squeaky Clean
3,419
49,325 (avg. 14.4)
1,996 (58.4%)
96 (2.8%)
Elon's Toy Car Elon's Toy Car
1,851
11,493 (avg. 6.2)
1,774 (95.8%)
19 (1.0%)
Play Your Cards! Play Your Cards!
5,199
51,070 (avg. 9.8)
4,092 (78.7%)
77 (1.5%)
Need for Speed Need for Speed
1,468
12,453 (avg. 8.5)
1,358 (92.5%)
26 (1.8%)
Remote Control Competition Remote Control Competition
1,339
13,603 (avg. 10.2)
1,015 (75.8%)
31 (2.3%)
Cars, Assemble! Cars, Assemble!
3,287
22,270 (avg. 6.8)
3,017 (91.8%)
38 (1.2%)
Log Levels Log Levels
8,294
69,460 (avg. 8.4)
5,200 (62.7%)
91 (1.1%)
Salary Calculator Salary Calculator
1,718
8,234 (avg. 4.8)
1,614 (93.9%)
10 (0.6%)
Football Match Reports Football Match Reports
1,204
4,207 (avg. 3.5)
1,175 (97.6%)
10 (0.8%)
Wizards and Warriors Wizards and Warriors
1,165
5,031 (avg. 4.3)
1,094 (93.9%)
12 (1.0%)

Build Test Runners

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Create Test Runners that have the single responsibility of taking a solution, running all tests and returning a standardized output.

Next goal: Get Test Runners to Version 3. Java is currently utilising a Version 2 Test Runner. Find out more.

Usage statistics

Total Test Runner Runs
930,955
Test Run Pass Rate
21.8% (203121)
Test Run Fail Rate
34.0% (316191)
Test Run Error Rate
44.2% (411643)

Build Analyzers

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Build an Analyzer for Java: Exercism's analyzers automatically assess student's submissions and provide mentor-style commentary.

Next goal: Build an Analyzer. Find out more.

Build Representers

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Build a Representer: a bit of code that has the single responsibility of taking a solution and returning a normalized representation of it.

Usage statistics

Total Representer Runs
128,886
Total Representation Comments Made
0
Feedback Given Frequency
0.0%

Create Practice Exercises

Learn More

Practice Exercises are exercises designed to allow students to solve an arbitrary problem, with the aim of them making use of the concepts they have learned so far.

Next goal: Implement 129 practice exercises. Find out more.

Usage statistics

116 active practice exercises
Started
Attempts
Completions
Mentoring requests
Hello World Hello World
64,333
123,153 (avg. 1.9)
42,168 (65.5%)
40 (0.1%)
Two Fer Two Fer
15,679
40,844 (avg. 2.6)
11,954 (76.2%)
3,725 (23.8%)
Hamming Hamming
6,199
16,766 (avg. 2.7)
4,993 (80.5%)
1,459 (23.5%)
Gigasecond Gigasecond
5,666
11,322 (avg. 2.0)
4,067 (71.8%)
1,327 (23.4%)
Scrabble Score Scrabble Score
4,066
12,150 (avg. 3.0)
3,326 (81.8%)
1,040 (25.6%)
Difference of Squares Difference of Squares
3,798
10,333 (avg. 2.7)
3,264 (85.9%)
661 (17.4%)
Secret Handshake Secret Handshake
2,600
9,022 (avg. 3.5)
1,899 (73.0%)
443 (17.0%)
Matrix Matrix
1,929
7,393 (avg. 3.8)
1,402 (72.7%)
293 (15.2%)
Triangle Triangle
1,854
5,988 (avg. 3.2)
1,542 (83.2%)
243 (13.1%)
Rotational Cipher Rotational Cipher
1,372
5,689 (avg. 4.1)
1,107 (80.7%)
195 (14.2%)
Saddle Points Saddle Points
1,042
3,330 (avg. 3.2)
683 (65.5%)
146 (14.0%)
Flatten Array Flatten Array
1,002
3,494 (avg. 3.5)
716 (71.5%)
117 (11.7%)
Word Count Word Count
1,887
7,782 (avg. 4.1)
1,499 (79.4%)
192 (10.2%)
Robot Name Robot Name
1,167
5,163 (avg. 4.4)
965 (82.7%)
125 (10.7%)
Binary Search Binary Search
686
2,853 (avg. 4.2)
498 (72.6%)
80 (11.7%)
Bank Account Bank Account
760
3,684 (avg. 4.8)
512 (67.4%)
74 (9.7%)
Linked List Linked List
749
2,484 (avg. 3.3)
526 (70.2%)
61 (8.1%)
Raindrops Raindrops
5,553
10,420 (avg. 1.9)
4,446 (80.1%)
208 (3.7%)
Isogram Isogram
3,305
8,748 (avg. 2.6)
2,500 (75.6%)
134 (4.1%)
Pig Latin Pig Latin
2,055
5,174 (avg. 2.5)
1,040 (50.6%)
57 (2.8%)
Anagram Anagram
2,486
5,734 (avg. 2.3)
1,739 (70.0%)
100 (4.0%)
Reverse String Reverse String
8,969
20,614 (avg. 2.3)
7,262 (81.0%)
214 (2.4%)
Darts Darts
3,190
7,288 (avg. 2.3)
2,350 (73.7%)
25 (0.8%)
D&D Character D&D Character
2,093
6,595 (avg. 3.2)
1,393 (66.6%)
23 (1.1%)
Grains Grains
1,711
8,264 (avg. 4.8)
1,330 (77.7%)
23 (1.3%)
Resistor Color Resistor Color
3,608
8,328 (avg. 2.3)
2,726 (75.6%)
42 (1.2%)
Resistor Color Duo Resistor Color Duo
2,301
4,842 (avg. 2.1)
1,832 (79.6%)
20 (0.9%)
Micro Blog Micro Blog
2,511
13,367 (avg. 5.3)
1,474 (58.7%)
32 (1.3%)
Protein Translation Protein Translation
2,011
3,851 (avg. 1.9)
1,514 (75.3%)
27 (1.3%)
Diamond Diamond
1,245
2,862 (avg. 2.3)
781 (62.7%)
10 (0.8%)
Proverb Proverb
1,871
3,656 (avg. 2.0)
1,436 (76.8%)
16 (0.9%)
Twelve Days Twelve Days
1,859
8,421 (avg. 4.5)
1,377 (74.1%)
18 (1.0%)
Bob Bob
1,315
4,464 (avg. 3.4)
1,063 (80.8%)
46 (3.5%)
Beer Song Beer Song
690
2,362 (avg. 3.4)
503 (72.9%)
10 (1.4%)
Food Chain Food Chain
514
1,209 (avg. 2.4)
318 (61.9%)
5 (1.0%)
House House
576
1,387 (avg. 2.4)
400 (69.4%)
3 (0.5%)
ISBN Verifier ISBN Verifier
1,509
3,159 (avg. 2.1)
1,116 (74.0%)
23 (1.5%)
Largest Series Product Largest Series Product
1,068
2,811 (avg. 2.6)
816 (76.4%)
5 (0.5%)
Luhn Luhn
1,574
4,353 (avg. 2.8)
1,173 (74.5%)
26 (1.7%)
Knapsack Knapsack
392
1,177 (avg. 3.0)
200 (51.0%)
4 (1.0%)
Nucleotide Count Nucleotide Count
1,616
3,478 (avg. 2.2)
1,460 (90.3%)
84 (5.2%)
Phone Number Phone Number
990
2,835 (avg. 2.9)
758 (76.6%)
20 (2.0%)
Series Series
601
1,199 (avg. 2.0)
482 (80.2%)
4 (0.7%)
Roman Numerals Roman Numerals
727
1,615 (avg. 2.2)
536 (73.7%)
6 (0.8%)
Allergies Allergies
793
1,690 (avg. 2.1)
595 (75.0%)
18 (2.3%)
Meetup Meetup
625
1,269 (avg. 2.0)
496 (79.4%)
10 (1.6%)
Yacht Yacht
1,113
3,183 (avg. 2.9)
665 (59.7%)
17 (1.5%)
Bowling Bowling
447
1,822 (avg. 4.1)
182 (40.7%)
6 (1.3%)
Minesweeper Minesweeper
503
1,472 (avg. 2.9)
302 (60.0%)
6 (1.2%)
Queen Attack Queen Attack
1,108
3,597 (avg. 3.2)
444 (40.1%)
14 (1.3%)
Dominoes Dominoes
557
1,189 (avg. 2.1)
118 (21.2%)
7 (1.3%)
Go Counting Go Counting
260
360 (avg. 1.4)
70 (26.9%)
0 (0.0%)
Markdown Markdown
470
744 (avg. 1.6)
157 (33.4%)
7 (1.5%)
Poker Poker
380
717 (avg. 1.9)
96 (25.3%)
2 (0.5%)
Word Search Word Search
475
796 (avg. 1.7)
125 (26.3%)
2 (0.4%)
Perfect Numbers Perfect Numbers
1,898
5,164 (avg. 2.7)
1,279 (67.4%)
25 (1.3%)
Say Say
795
2,428 (avg. 3.1)
232 (29.2%)
8 (1.0%)
Sieve Sieve
860
1,279 (avg. 1.5)
667 (77.6%)
15 (1.7%)
Sum of Multiples Sum of Multiples
1,296
2,627 (avg. 2.0)
958 (73.9%)
20 (1.5%)
Variable Length Quantity Variable Length Quantity
318
294 (avg. 0.9)
134 (42.1%)
0 (0.0%)
Alphametics Alphametics
290
391 (avg. 1.3)
84 (29.0%)
2 (0.7%)
Robot Simulator Robot Simulator
481
1,078 (avg. 2.2)
279 (58.0%)
5 (1.0%)
Wordy Wordy
311
683 (avg. 2.2)
158 (50.8%)
1 (0.3%)
Forth Forth
282
597 (avg. 2.1)
91 (32.3%)
4 (1.4%)
Kindergarten Garden Kindergarten Garden
548
733 (avg. 1.3)
389 (71.0%)
5 (0.9%)
Pascal's Triangle Pascal's Triangle
439
653 (avg. 1.5)
297 (67.7%)
0 (0.0%)
Spiral Matrix Spiral Matrix
298
499 (avg. 1.7)
168 (56.4%)
1 (0.3%)
Tournament Tournament
249
530 (avg. 2.1)
130 (52.2%)
0 (0.0%)
Transpose Transpose
296
878 (avg. 3.0)
142 (48.0%)
1 (0.3%)
Collatz Conjecture Collatz Conjecture
632
1,105 (avg. 1.7)
505 (79.9%)
7 (1.1%)
Error Handling Error Handling
679
4,169 (avg. 6.1)
306 (45.1%)
3 (0.4%)
Nth Prime Nth Prime
690
1,459 (avg. 2.1)
501 (72.6%)
7 (1.0%)
Prime Factors Prime Factors
522
1,192 (avg. 2.3)
381 (73.0%)
8 (1.5%)
Two Bucket Two Bucket
172
230 (avg. 1.3)
64 (37.2%)
1 (0.6%)
Complex Numbers Complex Numbers
249
430 (avg. 1.7)
142 (57.0%)
3 (1.2%)
Rational Numbers Rational Numbers
195
513 (avg. 2.6)
95 (48.7%)
2 (1.0%)
Pythagorean Triplet Pythagorean Triplet
636
4,264 (avg. 6.7)
253 (39.8%)
4 (0.6%)
Atbash Cipher Atbash Cipher
420
1,016 (avg. 2.4)
312 (74.3%)
2 (0.5%)
Run-Length Encoding Run-Length Encoding
359
787 (avg. 2.2)
234 (65.2%)
5 (1.4%)
Affine Cipher Affine Cipher
156
520 (avg. 3.3)
78 (50.0%)
2 (1.3%)
Rail Fence Cipher Rail Fence Cipher
171
226 (avg. 1.3)
87 (50.9%)
0 (0.0%)
Crypto Square Crypto Square
264
459 (avg. 1.7)
172 (65.2%)
2 (0.8%)
Simple Cipher Simple Cipher
280
309 (avg. 1.1)
164 (58.6%)
2 (0.7%)
All Your Base All Your Base
242
505 (avg. 2.1)
143 (59.1%)
1 (0.4%)
Clock Clock
257
498 (avg. 1.9)
141 (54.9%)
1 (0.4%)
Zebra Puzzle Zebra Puzzle
177
111 (avg. 0.6)
57 (32.2%)
0 (0.0%)
Palindrome Products Palindrome Products
220
423 (avg. 1.9)
106 (48.2%)
1 (0.5%)
Matching Brackets Matching Brackets
373
698 (avg. 1.9)
251 (67.3%)
3 (0.8%)
Book Store Book Store
261
374 (avg. 1.4)
84 (32.2%)
1 (0.4%)
Change Change
261
450 (avg. 1.7)
91 (34.9%)
2 (0.8%)
ETL ETL
1,527
2,023 (avg. 1.3)
1,432 (93.8%)
127 (8.3%)
Grade School Grade School
517
906 (avg. 1.8)
381 (73.7%)
18 (3.5%)
Grep Grep
302
603 (avg. 2.0)
135 (44.7%)
0 (0.0%)
REST API REST API
294
481 (avg. 1.6)
49 (16.7%)
0 (0.0%)
OCR Numbers OCR Numbers
235
257 (avg. 1.1)
103 (43.8%)
1 (0.4%)
Rectangles Rectangles
187
267 (avg. 1.4)
82 (43.9%)
2 (1.1%)
Binary Search Tree Binary Search Tree
315
562 (avg. 1.8)
149 (47.3%)
2 (0.6%)
Parallel Letter Frequency Parallel Letter Frequency
233
464 (avg. 2.0)
131 (56.2%)
1 (0.4%)
Simple Linked List Simple Linked List
334
1,370 (avg. 4.1)
185 (55.4%)
4 (1.2%)
Sublist Sublist
249
662 (avg. 2.7)
149 (59.8%)
0 (0.0%)
Tree Building Tree Building
155
223 (avg. 1.4)
53 (34.2%)
1 (0.6%)
Zipper Zipper
140
250 (avg. 1.8)
49 (35.0%)
0 (0.0%)
Circular Buffer Circular Buffer
274
484 (avg. 1.8)
137 (50.0%)
0 (0.0%)
Diffie-Hellman Diffie-Hellman
186
266 (avg. 1.4)
89 (47.8%)
0 (0.0%)
Hangman Hangman
125
274 (avg. 2.2)
17 (13.6%)
1 (0.8%)
List Ops List Ops
230
467 (avg. 2.0)
112 (48.7%)
2 (0.9%)
Custom Set Custom Set
254
437 (avg. 1.7)
105 (41.3%)
1 (0.4%)
Satellite Satellite
135
301 (avg. 2.2)
46 (34.1%)
1 (0.7%)
Leap Leap
2,506
3,511 (avg. 1.4)
1,965 (78.4%)
25 (1.0%)
Armstrong Numbers Armstrong Numbers
3,422
5,034 (avg. 1.5)
2,553 (74.6%)
79 (2.3%)
RNA Transcription RNA Transcription
4,678
9,350 (avg. 2.0)
3,864 (82.6%)
209 (4.5%)
Acronym Acronym
2,604
5,277 (avg. 2.0)
2,043 (78.5%)
58 (2.2%)
Pangram Pangram
3,701
6,116 (avg. 1.7)
3,065 (82.8%)
149 (4.0%)
Space Age Space Age
2,800
3,894 (avg. 1.4)
2,172 (77.6%)
46 (1.6%)
Connect Connect
130
752 (avg. 5.8)
54 (41.5%)
3 (2.3%)
SGF Parsing SGF Parsing
18
327 (avg. 18.2)
7 (38.9%)
0 (0.0%)
6 deprecated practice exercises
Started
Attempts
Completions
Mentoring requests
Accumulate Accumulate
110
138 (avg. 1.3)
107 (97.3%)
5 (4.5%)
Binary Binary
136
180 (avg. 1.3)
133 (97.8%)
6 (4.4%)
Hexadecimal Hexadecimal
58
72 (avg. 1.2)
55 (94.8%)
7 (12.1%)
Octal Octal
59
69 (avg. 1.2)
56 (94.9%)
2 (3.4%)
Strain Strain
111
137 (avg. 1.2)
107 (96.4%)
5 (4.5%)
Trinary Trinary
71
83 (avg. 1.2)
68 (95.8%)
1 (1.4%)
13 unimplemented practice exercises
Bottle Song Bottle Song
DOT DSL DOT DSL
High Scores High Scores
Killer Sudoku Helper Killer Sudoku Helper
Ledger Ledger
Lens Person Lens Person
POV POV
PaaS I/O PaaS I/O
React React
Resistor Color Trio Resistor Color Trio
Scale Generator Scale Generator
Square Root Square Root
State of Tic-Tac-Toe State of Tic-Tac-Toe