Java
Java
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132,543
students have developed their Java skills on Exercism.

Students
132,543
Submissions
1,311,942
Mentoring Discussions
13,439

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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
19,178 learnt
Bo
Booleans
10,419 learnt
Ar
Arrays
4,211 learnt
Fo
For Loops
4,211 learnt
Fo
For-Each Loops
4,211 learnt
Ge
Generic Types
2,719 learnt
Li
Lists
2,719 learnt
Ch
Chars
2,753 learnt
Cl
Classes
2,365 learnt
Co
Conditionals If
5,520 learnt
Co
Constructors
1,816 learnt
In
Interfaces
1,314 learnt
Nu
Numbers
3,965 learnt
St
Strings
7,071 learnt
Te
Ternary Operators
2,128 learnt
Sw
Switch Statements
1,562 learnt
In
Inheritance
1,448 learnt
14 active learning exercises
Started
Attempts
Completions
Mentoring requests
Cook your lasagna Cook your lasagna
31,275
151,963 (avg. 4.9)
19,178 (61.3%)
183 (0.6%)
Annalyn's Infiltration Annalyn's Infiltration
13,704
104,503 (avg. 7.6)
10,419 (76.0%)
114 (0.8%)
Bird Watcher Bird Watcher
4,809
61,933 (avg. 12.9)
4,211 (87.6%)
52 (1.1%)
Karl's Languages Karl's Languages
2,902
12,864 (avg. 4.4)
2,719 (93.7%)
19 (0.7%)
Squeaky Clean Squeaky Clean
4,651
66,012 (avg. 14.2)
2,753 (59.2%)
118 (2.5%)
Elon's Toy Car Elon's Toy Car
2,484
15,258 (avg. 6.1)
2,365 (95.2%)
24 (1.0%)
Play Your Cards! Play Your Cards!
7,030
68,185 (avg. 9.7)
5,520 (78.5%)
89 (1.3%)
Need for Speed Need for Speed
1,960
16,189 (avg. 8.3)
1,816 (92.7%)
27 (1.4%)
Remote Control Competition Remote Control Competition
1,762
17,411 (avg. 9.9)
1,314 (74.6%)
35 (2.0%)
Cars, Assemble! Cars, Assemble!
4,272
27,824 (avg. 6.5)
3,965 (92.8%)
40 (0.9%)
Log Levels Log Levels
11,241
94,031 (avg. 8.4)
7,071 (62.9%)
108 (1.0%)
Salary Calculator Salary Calculator
2,263
10,707 (avg. 4.7)
2,128 (94.0%)
11 (0.5%)
Football Match Reports Football Match Reports
1,595
5,490 (avg. 3.4)
1,562 (97.9%)
12 (0.8%)
Wizards and Warriors Wizards and Warriors
1,543
6,729 (avg. 4.4)
1,448 (93.8%)
14 (0.9%)

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
1,230,803
Test Run Pass Rate
20.8% (255409)
Test Run Fail Rate
34.5% (424667)
Test Run Error Rate
44.7% (550727)

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
174,306
Total Representation Comments Made
0
Feedback Given Frequency
0.0%

Create Practice Exercises

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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

119 active practice exercises
Started
Attempts
Completions
Mentoring requests
Hello World Hello World
81,979
165,786 (avg. 2.0)
52,876 (64.5%)
40 (0.0%)
Two Fer Two Fer
17,710
50,117 (avg. 2.8)
13,605 (76.8%)
3,803 (21.5%)
Hamming Hamming
6,570
19,283 (avg. 2.9)
5,332 (81.2%)
1,467 (22.3%)
Gigasecond Gigasecond
6,407
13,467 (avg. 2.1)
4,530 (70.7%)
1,335 (20.8%)
Scrabble Score Scrabble Score
4,589
14,944 (avg. 3.3)
3,788 (82.5%)
1,055 (23.0%)
Difference of Squares Difference of Squares
4,416
12,892 (avg. 2.9)
3,816 (86.4%)
672 (15.2%)
Secret Handshake Secret Handshake
2,945
11,058 (avg. 3.8)
2,168 (73.6%)
449 (15.2%)
Matrix Matrix
2,221
9,263 (avg. 4.2)
1,633 (73.5%)
301 (13.6%)
Triangle Triangle
2,092
7,166 (avg. 3.4)
1,762 (84.2%)
246 (11.8%)
Rotational Cipher Rotational Cipher
1,658
7,236 (avg. 4.4)
1,356 (81.8%)
199 (12.0%)
Saddle Points Saddle Points
1,201
4,146 (avg. 3.5)
797 (66.4%)
150 (12.5%)
Flatten Array Flatten Array
1,136
4,383 (avg. 3.9)
832 (73.2%)
122 (10.7%)
Word Count Word Count
2,115
10,239 (avg. 4.8)
1,677 (79.3%)
196 (9.3%)
Robot Name Robot Name
1,310
6,491 (avg. 5.0)
1,089 (83.1%)
130 (9.9%)
Binary Search Binary Search
824
3,931 (avg. 4.8)
614 (74.5%)
84 (10.2%)
Bank Account Bank Account
920
4,780 (avg. 5.2)
639 (69.5%)
79 (8.6%)
Linked List Linked List
909
3,277 (avg. 3.6)
660 (72.6%)
66 (7.3%)
Raindrops Raindrops
6,033
12,424 (avg. 2.1)
4,905 (81.3%)
219 (3.6%)
Isogram Isogram
3,662
11,028 (avg. 3.0)
2,820 (77.0%)
148 (4.0%)
Pig Latin Pig Latin
2,211
6,935 (avg. 3.1)
1,141 (51.6%)
61 (2.8%)
Anagram Anagram
2,646
6,957 (avg. 2.6)
1,864 (70.4%)
104 (3.9%)
Reverse String Reverse String
10,288
26,367 (avg. 2.6)
8,409 (81.7%)
242 (2.4%)
Darts Darts
3,547
9,095 (avg. 2.6)
2,657 (74.9%)
28 (0.8%)
D&D Character D&D Character
2,341
9,184 (avg. 3.9)
1,553 (66.3%)
25 (1.1%)
Grains Grains
1,989
10,706 (avg. 5.4)
1,560 (78.4%)
25 (1.3%)
Resistor Color Resistor Color
3,994
10,443 (avg. 2.6)
3,027 (75.8%)
49 (1.2%)
Resistor Color Duo Resistor Color Duo
2,590
6,071 (avg. 2.3)
2,071 (80.0%)
25 (1.0%)
Micro Blog Micro Blog
3,461
18,981 (avg. 5.5)
2,066 (59.7%)
47 (1.4%)
Protein Translation Protein Translation
2,202
4,988 (avg. 2.3)
1,678 (76.2%)
31 (1.4%)
Diamond Diamond
1,398
3,622 (avg. 2.6)
888 (63.5%)
16 (1.1%)
Proverb Proverb
2,046
4,590 (avg. 2.2)
1,584 (77.4%)
22 (1.1%)
Twelve Days Twelve Days
2,012
9,450 (avg. 4.7)
1,495 (74.3%)
19 (0.9%)
Bob Bob
1,422
5,515 (avg. 3.9)
1,147 (80.7%)
47 (3.3%)
Beer Song Beer Song
773
2,832 (avg. 3.7)
575 (74.4%)
13 (1.7%)
Food Chain Food Chain
575
1,520 (avg. 2.6)
370 (64.3%)
7 (1.2%)
House House
650
1,878 (avg. 2.9)
456 (70.2%)
5 (0.8%)
ISBN Verifier ISBN Verifier
1,605
3,825 (avg. 2.4)
1,203 (75.0%)
26 (1.6%)
Largest Series Product Largest Series Product
1,144
3,585 (avg. 3.1)
884 (77.3%)
10 (0.9%)
Luhn Luhn
1,680
5,370 (avg. 3.2)
1,271 (75.7%)
28 (1.7%)
Knapsack Knapsack
447
1,767 (avg. 4.0)
241 (53.9%)
5 (1.1%)
Nucleotide Count Nucleotide Count
1,685
3,884 (avg. 2.3)
1,519 (90.1%)
85 (5.0%)
Phone Number Phone Number
1,040
3,596 (avg. 3.5)
803 (77.2%)
20 (1.9%)
Series Series
649
1,383 (avg. 2.1)
525 (80.9%)
7 (1.1%)
Roman Numerals Roman Numerals
778
1,798 (avg. 2.3)
576 (74.0%)
6 (0.8%)
Allergies Allergies
849
1,924 (avg. 2.3)
638 (75.1%)
18 (2.1%)
Meetup Meetup
665
1,438 (avg. 2.2)
529 (79.5%)
10 (1.5%)
Yacht Yacht
1,163
3,489 (avg. 3.0)
709 (61.0%)
22 (1.9%)
Bowling Bowling
532
2,585 (avg. 4.9)
219 (41.2%)
6 (1.1%)
Minesweeper Minesweeper
551
1,741 (avg. 3.2)
339 (61.5%)
7 (1.3%)
Queen Attack Queen Attack
1,427
4,468 (avg. 3.1)
512 (35.9%)
18 (1.3%)
Dominoes Dominoes
710
1,447 (avg. 2.0)
154 (21.7%)
7 (1.0%)
Go Counting Go Counting
324
497 (avg. 1.5)
88 (27.2%)
0 (0.0%)
Markdown Markdown
553
889 (avg. 1.6)
195 (35.3%)
8 (1.4%)
Poker Poker
458
1,036 (avg. 2.3)
118 (25.8%)
2 (0.4%)
Word Search Word Search
552
945 (avg. 1.7)
151 (27.4%)
3 (0.5%)
Perfect Numbers Perfect Numbers
2,220
6,517 (avg. 2.9)
1,409 (63.5%)
30 (1.4%)
Say Say
1,062
2,966 (avg. 2.8)
297 (28.0%)
12 (1.1%)
Sieve Sieve
909
1,454 (avg. 1.6)
703 (77.3%)
17 (1.9%)
Sum of Multiples Sum of Multiples
1,401
3,200 (avg. 2.3)
1,018 (72.7%)
26 (1.9%)
Variable Length Quantity Variable Length Quantity
348
372 (avg. 1.1)
153 (44.0%)
0 (0.0%)
Alphametics Alphametics
327
503 (avg. 1.5)
95 (29.1%)
2 (0.6%)
Robot Simulator Robot Simulator
546
1,431 (avg. 2.6)
320 (58.6%)
6 (1.1%)
Wordy Wordy
353
837 (avg. 2.4)
189 (53.5%)
2 (0.6%)
Forth Forth
326
672 (avg. 2.1)
104 (31.9%)
5 (1.5%)
Kindergarten Garden Kindergarten Garden
583
813 (avg. 1.4)
416 (71.4%)
6 (1.0%)
Pascal's Triangle Pascal's Triangle
476
781 (avg. 1.6)
319 (67.0%)
1 (0.2%)
Spiral Matrix Spiral Matrix
338
588 (avg. 1.7)
192 (56.8%)
2 (0.6%)
Tournament Tournament
291
680 (avg. 2.3)
153 (52.6%)
1 (0.3%)
Transpose Transpose
340
1,152 (avg. 3.4)
164 (48.2%)
1 (0.3%)
Collatz Conjecture Collatz Conjecture
674
1,232 (avg. 1.8)
539 (80.0%)
10 (1.5%)
Error Handling Error Handling
727
4,397 (avg. 6.0)
327 (45.0%)
4 (0.6%)
Nth Prime Nth Prime
741
1,688 (avg. 2.3)
537 (72.5%)
9 (1.2%)
Prime Factors Prime Factors
567
1,347 (avg. 2.4)
412 (72.7%)
8 (1.4%)
Two Bucket Two Bucket
203
267 (avg. 1.3)
76 (37.4%)
2 (1.0%)
Complex Numbers Complex Numbers
290
606 (avg. 2.1)
169 (58.3%)
3 (1.0%)
Rational Numbers Rational Numbers
226
859 (avg. 3.8)
116 (51.3%)
2 (0.9%)
Pythagorean Triplet Pythagorean Triplet
683
4,594 (avg. 6.7)
271 (39.7%)
4 (0.6%)
Atbash Cipher Atbash Cipher
454
1,277 (avg. 2.8)
338 (74.4%)
3 (0.7%)
Run-Length Encoding Run-Length Encoding
391
932 (avg. 2.4)
252 (64.5%)
6 (1.5%)
Affine Cipher Affine Cipher
176
554 (avg. 3.1)
91 (51.7%)
2 (1.1%)
Rail Fence Cipher Rail Fence Cipher
195
274 (avg. 1.4)
102 (52.3%)
0 (0.0%)
Crypto Square Crypto Square
281
588 (avg. 2.1)
181 (64.4%)
2 (0.7%)
Simple Cipher Simple Cipher
307
452 (avg. 1.5)
182 (59.3%)
3 (1.0%)
All Your Base All Your Base
272
572 (avg. 2.1)
159 (58.5%)
1 (0.4%)
Clock Clock
289
661 (avg. 2.3)
170 (58.8%)
1 (0.3%)
Zebra Puzzle Zebra Puzzle
209
266 (avg. 1.3)
70 (33.5%)
0 (0.0%)
Palindrome Products Palindrome Products
260
585 (avg. 2.3)
129 (49.6%)
1 (0.4%)
Matching Brackets Matching Brackets
404
916 (avg. 2.3)
273 (67.6%)
5 (1.2%)
Book Store Book Store
291
406 (avg. 1.4)
94 (32.3%)
1 (0.3%)
Change Change
296
558 (avg. 1.9)
105 (35.5%)
2 (0.7%)
ETL ETL
1,562
2,110 (avg. 1.4)
1,458 (93.3%)
127 (8.1%)
Grade School Grade School
553
1,137 (avg. 2.1)
407 (73.6%)
18 (3.3%)
Grep Grep
326
672 (avg. 2.1)
148 (45.4%)
1 (0.3%)
REST API REST API
344
571 (avg. 1.7)
59 (17.2%)
0 (0.0%)
OCR Numbers OCR Numbers
255
313 (avg. 1.2)
116 (45.5%)
1 (0.4%)
Rectangles Rectangles
207
342 (avg. 1.7)
93 (44.9%)
2 (1.0%)
Binary Search Tree Binary Search Tree
348
737 (avg. 2.1)
170 (48.9%)
3 (0.9%)
Parallel Letter Frequency Parallel Letter Frequency
250
485 (avg. 1.9)
144 (57.6%)
1 (0.4%)
Simple Linked List Simple Linked List
371
1,481 (avg. 4.0)
205 (55.3%)
6 (1.6%)
Sublist Sublist
275
739 (avg. 2.7)
169 (61.5%)
0 (0.0%)
Tree Building Tree Building
174
237 (avg. 1.4)
62 (35.6%)
1 (0.6%)
Zipper Zipper
155
269 (avg. 1.7)
57 (36.8%)
0 (0.0%)
Circular Buffer Circular Buffer
303
531 (avg. 1.8)
155 (51.2%)
0 (0.0%)
Diffie-Hellman Diffie-Hellman
208
289 (avg. 1.4)
102 (49.0%)
1 (0.5%)
Hangman Hangman
155
313 (avg. 2.0)
26 (16.8%)
4 (2.6%)
List Ops List Ops
253
526 (avg. 2.1)
123 (48.6%)
2 (0.8%)
Custom Set Custom Set
276
488 (avg. 1.8)
115 (41.7%)
1 (0.4%)
Satellite Satellite
150
328 (avg. 2.2)
53 (35.3%)
1 (0.7%)
Leap Leap
2,663
3,950 (avg. 1.5)
2,090 (78.5%)
28 (1.1%)
Armstrong Numbers Armstrong Numbers
3,566
5,550 (avg. 1.6)
2,658 (74.5%)
81 (2.3%)
RNA Transcription RNA Transcription
4,789
9,736 (avg. 2.0)
3,953 (82.5%)
212 (4.4%)
Acronym Acronym
2,745
6,235 (avg. 2.3)
2,133 (77.7%)
63 (2.3%)
Pangram Pangram
3,842
6,813 (avg. 1.8)
3,164 (82.4%)
153 (4.0%)
Space Age Space Age
2,967
4,402 (avg. 1.5)
2,264 (76.3%)
51 (1.7%)
Connect Connect
182
892 (avg. 4.9)
84 (46.2%)
4 (2.2%)
SGF Parsing SGF Parsing
33
341 (avg. 10.3)
14 (42.4%)
2 (6.1%)
POV POV
20
10 (avg. 0.5)
6 (30.0%)
0 (0.0%)
Ledger Ledger
38
32 (avg. 0.8)
11 (28.9%)
2 (5.3%)
High Scores High Scores
111
926 (avg. 8.3)
88 (79.3%)
1 (0.9%)
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%)
10 unimplemented practice exercises
Bottle Song Bottle Song
View dataThe link opens in a new window or tab
DOT DSL DOT DSL
View dataThe link opens in a new window or tab
Killer Sudoku Helper Killer Sudoku Helper
View dataThe link opens in a new window or tab
Lens Person Lens Person
View dataThe link opens in a new window or tab
PaaS I/O PaaS I/O
View dataThe link opens in a new window or tab
React React
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Resistor Color Trio Resistor Color Trio
View dataThe link opens in a new window or tab
Scale Generator Scale Generator
View dataThe link opens in a new window or tab
Square Root Square Root
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State of Tic-Tac-Toe State of Tic-Tac-Toe
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