Java
Java
AboutSyllabusExercisesBuild Status

134,736
students have developed their Java skills on Exercism.

Students
134,736
Submissions
1,355,823
Mentoring Discussions
13,531

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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
19,894 learnt
Bo
Booleans
10,828 learnt
Ar
Arrays
4,373 learnt
Fo
For Loops
4,373 learnt
Fo
For-Each Loops
4,373 learnt
Ge
Generic Types
2,838 learnt
Li
Lists
2,838 learnt
Ch
Chars
2,878 learnt
Cl
Classes
2,461 learnt
Co
Conditionals If
5,766 learnt
Co
Constructors
1,893 learnt
In
Interfaces
1,376 learnt
Nu
Numbers
4,119 learnt
St
Strings
7,365 learnt
Te
Ternary Operators
2,219 learnt
Sw
Switch Statements
1,637 learnt
In
Inheritance
1,516 learnt
14 active learning exercises
Started
Attempts
Completions
Mentoring requests
Cook your lasagna Cook your lasagna
32,292
156,964 (avg. 4.9)
19,894 (61.6%)
189 (0.6%)
Annalyn's Infiltration Annalyn's Infiltration
14,241
108,883 (avg. 7.6)
10,828 (76.0%)
117 (0.8%)
Bird Watcher Bird Watcher
4,999
64,063 (avg. 12.8)
4,373 (87.5%)
54 (1.1%)
Karl's Languages Karl's Languages
3,029
13,371 (avg. 4.4)
2,838 (93.7%)
19 (0.6%)
Squeaky Clean Squeaky Clean
4,852
68,595 (avg. 14.1)
2,878 (59.3%)
121 (2.5%)
Elon's Toy Car Elon's Toy Car
2,586
15,812 (avg. 6.1)
2,461 (95.2%)
24 (0.9%)
Play Your Cards! Play Your Cards!
7,332
71,277 (avg. 9.7)
5,766 (78.6%)
92 (1.3%)
Need for Speed Need for Speed
2,043
16,727 (avg. 8.2)
1,893 (92.7%)
27 (1.3%)
Remote Control Competition Remote Control Competition
1,846
18,167 (avg. 9.8)
1,376 (74.5%)
35 (1.9%)
Cars, Assemble! Cars, Assemble!
4,436
28,624 (avg. 6.5)
4,119 (92.9%)
40 (0.9%)
Log Levels Log Levels
11,701
97,441 (avg. 8.3)
7,365 (62.9%)
114 (1.0%)
Salary Calculator Salary Calculator
2,358
11,074 (avg. 4.7)
2,219 (94.1%)
11 (0.5%)
Football Match Reports Football Match Reports
1,671
5,711 (avg. 3.4)
1,637 (98.0%)
12 (0.7%)
Wizards and Warriors Wizards and Warriors
1,613
7,086 (avg. 4.4)
1,516 (94.0%)
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
1,274,364
Test Run Pass Rate
20.7% (263619)
Test Run Fail Rate
34.6% (440353)
Test Run Error Rate
44.8% (570392)

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
181,886
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
83,828
170,110 (avg. 2.0)
54,125 (64.6%)
40 (0.0%)
Two Fer Two Fer
18,048
51,969 (avg. 2.9)
13,885 (76.9%)
3,819 (21.2%)
Hamming Hamming
6,646
19,788 (avg. 3.0)
5,397 (81.2%)
1,468 (22.1%)
Gigasecond Gigasecond
6,548
13,822 (avg. 2.1)
4,621 (70.6%)
1,335 (20.4%)
Scrabble Score Scrabble Score
4,672
15,341 (avg. 3.3)
3,862 (82.7%)
1,056 (22.6%)
Difference of Squares Difference of Squares
4,528
13,403 (avg. 3.0)
3,920 (86.6%)
675 (14.9%)
Secret Handshake Secret Handshake
3,002
11,419 (avg. 3.8)
2,208 (73.6%)
451 (15.0%)
Matrix Matrix
2,281
9,577 (avg. 4.2)
1,681 (73.7%)
303 (13.3%)
Triangle Triangle
2,134
7,313 (avg. 3.4)
1,804 (84.5%)
247 (11.6%)
Rotational Cipher Rotational Cipher
1,714
7,550 (avg. 4.4)
1,408 (82.1%)
202 (11.8%)
Saddle Points Saddle Points
1,235
4,227 (avg. 3.4)
830 (67.2%)
150 (12.1%)
Flatten Array Flatten Array
1,173
4,477 (avg. 3.8)
868 (74.0%)
122 (10.4%)
Word Count Word Count
2,161
10,426 (avg. 4.8)
1,716 (79.4%)
198 (9.2%)
Robot Name Robot Name
1,353
6,620 (avg. 4.9)
1,129 (83.4%)
131 (9.7%)
Binary Search Binary Search
862
4,144 (avg. 4.8)
649 (75.3%)
84 (9.7%)
Bank Account Bank Account
963
4,900 (avg. 5.1)
675 (70.1%)
79 (8.2%)
Linked List Linked List
956
3,399 (avg. 3.6)
699 (73.1%)
66 (6.9%)
Raindrops Raindrops
6,122
12,775 (avg. 2.1)
4,996 (81.6%)
219 (3.6%)
Isogram Isogram
3,747
11,453 (avg. 3.1)
2,903 (77.5%)
149 (4.0%)
Pig Latin Pig Latin
2,262
7,074 (avg. 3.1)
1,184 (52.3%)
63 (2.8%)
Anagram Anagram
2,707
7,150 (avg. 2.6)
1,915 (70.7%)
105 (3.9%)
Reverse String Reverse String
10,526
27,335 (avg. 2.6)
8,624 (81.9%)
250 (2.4%)
Darts Darts
3,637
9,390 (avg. 2.6)
2,738 (75.3%)
31 (0.9%)
D&D Character D&D Character
2,396
9,716 (avg. 4.1)
1,604 (66.9%)
28 (1.2%)
Grains Grains
2,059
11,016 (avg. 5.4)
1,621 (78.7%)
25 (1.2%)
Resistor Color Resistor Color
4,075
10,695 (avg. 2.6)
3,095 (76.0%)
52 (1.3%)
Resistor Color Duo Resistor Color Duo
2,658
6,271 (avg. 2.4)
2,132 (80.2%)
25 (0.9%)
Micro Blog Micro Blog
3,629
19,815 (avg. 5.5)
2,173 (59.9%)
49 (1.4%)
Protein Translation Protein Translation
2,248
5,145 (avg. 2.3)
1,719 (76.5%)
32 (1.4%)
Diamond Diamond
1,440
3,844 (avg. 2.7)
919 (63.8%)
19 (1.3%)
Proverb Proverb
2,093
4,768 (avg. 2.3)
1,628 (77.8%)
24 (1.1%)
Twelve Days Twelve Days
2,057
9,689 (avg. 4.7)
1,526 (74.2%)
23 (1.1%)
Bob Bob
1,447
5,615 (avg. 3.9)
1,171 (80.9%)
47 (3.2%)
Beer Song Beer Song
792
2,863 (avg. 3.6)
592 (74.7%)
13 (1.6%)
Food Chain Food Chain
594
1,547 (avg. 2.6)
389 (65.5%)
7 (1.2%)
House House
668
1,912 (avg. 2.9)
473 (70.8%)
5 (0.7%)
ISBN Verifier ISBN Verifier
1,634
3,975 (avg. 2.4)
1,228 (75.2%)
26 (1.6%)
Largest Series Product Largest Series Product
1,170
3,715 (avg. 3.2)
910 (77.8%)
12 (1.0%)
Luhn Luhn
1,711
5,602 (avg. 3.3)
1,300 (76.0%)
29 (1.7%)
Knapsack Knapsack
474
1,870 (avg. 3.9)
261 (55.1%)
5 (1.1%)
Nucleotide Count Nucleotide Count
1,704
3,926 (avg. 2.3)
1,537 (90.2%)
85 (5.0%)
Phone Number Phone Number
1,061
3,657 (avg. 3.4)
822 (77.5%)
21 (2.0%)
Series Series
674
1,432 (avg. 2.1)
548 (81.3%)
7 (1.0%)
Roman Numerals Roman Numerals
801
1,844 (avg. 2.3)
600 (74.9%)
7 (0.9%)
Allergies Allergies
871
1,986 (avg. 2.3)
660 (75.8%)
19 (2.2%)
Meetup Meetup
685
1,511 (avg. 2.2)
549 (80.1%)
10 (1.5%)
Yacht Yacht
1,182
3,539 (avg. 3.0)
726 (61.4%)
22 (1.9%)
Bowling Bowling
558
2,737 (avg. 4.9)
239 (42.8%)
7 (1.3%)
Minesweeper Minesweeper
570
1,782 (avg. 3.1)
358 (62.8%)
7 (1.2%)
Queen Attack Queen Attack
1,488
4,848 (avg. 3.3)
522 (35.1%)
19 (1.3%)
Dominoes Dominoes
731
1,472 (avg. 2.0)
158 (21.6%)
7 (1.0%)
Go Counting Go Counting
332
509 (avg. 1.5)
94 (28.3%)
0 (0.0%)
Markdown Markdown
571
937 (avg. 1.6)
201 (35.2%)
9 (1.6%)
Poker Poker
465
1,066 (avg. 2.3)
121 (26.0%)
2 (0.4%)
Word Search Word Search
571
992 (avg. 1.7)
158 (27.7%)
3 (0.5%)
Perfect Numbers Perfect Numbers
2,268
6,609 (avg. 2.9)
1,427 (62.9%)
30 (1.3%)
Say Say
1,099
3,051 (avg. 2.8)
307 (27.9%)
13 (1.2%)
Sieve Sieve
916
1,470 (avg. 1.6)
710 (77.5%)
17 (1.9%)
Sum of Multiples Sum of Multiples
1,412
3,262 (avg. 2.3)
1,024 (72.5%)
26 (1.8%)
Variable Length Quantity Variable Length Quantity
355
397 (avg. 1.1)
157 (44.2%)
0 (0.0%)
Alphametics Alphametics
332
509 (avg. 1.5)
95 (28.6%)
2 (0.6%)
Robot Simulator Robot Simulator
552
1,475 (avg. 2.7)
324 (58.7%)
6 (1.1%)
Wordy Wordy
360
840 (avg. 2.3)
192 (53.3%)
2 (0.6%)
Forth Forth
330
673 (avg. 2.0)
105 (31.8%)
5 (1.5%)
Kindergarten Garden Kindergarten Garden
588
818 (avg. 1.4)
420 (71.4%)
6 (1.0%)
Pascal's Triangle Pascal's Triangle
484
806 (avg. 1.7)
325 (67.1%)
2 (0.4%)
Spiral Matrix Spiral Matrix
345
595 (avg. 1.7)
197 (57.1%)
2 (0.6%)
Tournament Tournament
298
687 (avg. 2.3)
156 (52.3%)
1 (0.3%)
Transpose Transpose
346
1,187 (avg. 3.4)
168 (48.6%)
1 (0.3%)
Collatz Conjecture Collatz Conjecture
681
1,244 (avg. 1.8)
545 (80.0%)
10 (1.5%)
Error Handling Error Handling
743
4,507 (avg. 6.1)
335 (45.1%)
4 (0.5%)
Nth Prime Nth Prime
758
1,739 (avg. 2.3)
550 (72.6%)
9 (1.2%)
Prime Factors Prime Factors
575
1,361 (avg. 2.4)
419 (72.9%)
8 (1.4%)
Two Bucket Two Bucket
204
268 (avg. 1.3)
77 (37.7%)
2 (1.0%)
Complex Numbers Complex Numbers
294
620 (avg. 2.1)
171 (58.2%)
3 (1.0%)
Rational Numbers Rational Numbers
227
859 (avg. 3.8)
116 (51.1%)
2 (0.9%)
Pythagorean Triplet Pythagorean Triplet
695
4,675 (avg. 6.7)
273 (39.3%)
4 (0.6%)
Atbash Cipher Atbash Cipher
459
1,310 (avg. 2.9)
343 (74.7%)
3 (0.7%)
Run-Length Encoding Run-Length Encoding
396
937 (avg. 2.4)
256 (64.6%)
6 (1.5%)
Affine Cipher Affine Cipher
179
561 (avg. 3.1)
93 (52.0%)
2 (1.1%)
Rail Fence Cipher Rail Fence Cipher
198
275 (avg. 1.4)
103 (52.0%)
0 (0.0%)
Crypto Square Crypto Square
283
595 (avg. 2.1)
183 (64.7%)
2 (0.7%)
Simple Cipher Simple Cipher
307
452 (avg. 1.5)
182 (59.3%)
3 (1.0%)
All Your Base All Your Base
276
591 (avg. 2.1)
162 (58.7%)
1 (0.4%)
Clock Clock
297
693 (avg. 2.3)
174 (58.6%)
1 (0.3%)
Zebra Puzzle Zebra Puzzle
212
273 (avg. 1.3)
72 (34.0%)
0 (0.0%)
Palindrome Products Palindrome Products
262
587 (avg. 2.2)
130 (49.6%)
1 (0.4%)
Matching Brackets Matching Brackets
406
920 (avg. 2.3)
277 (68.2%)
5 (1.2%)
Book Store Book Store
292
408 (avg. 1.4)
96 (32.9%)
1 (0.3%)
Change Change
302
567 (avg. 1.9)
105 (34.8%)
2 (0.7%)
ETL ETL
1,566
2,115 (avg. 1.4)
1,461 (93.3%)
127 (8.1%)
Grade School Grade School
560
1,162 (avg. 2.1)
412 (73.6%)
19 (3.4%)
Grep Grep
329
674 (avg. 2.0)
150 (45.6%)
1 (0.3%)
REST API REST API
349
581 (avg. 1.7)
61 (17.5%)
0 (0.0%)
OCR Numbers OCR Numbers
256
316 (avg. 1.2)
118 (46.1%)
1 (0.4%)
Rectangles Rectangles
210
350 (avg. 1.7)
96 (45.7%)
2 (1.0%)
Binary Search Tree Binary Search Tree
354
760 (avg. 2.1)
172 (48.6%)
3 (0.8%)
Parallel Letter Frequency Parallel Letter Frequency
255
490 (avg. 1.9)
148 (58.0%)
1 (0.4%)
Simple Linked List Simple Linked List
387
1,607 (avg. 4.2)
214 (55.3%)
6 (1.6%)
Sublist Sublist
282
751 (avg. 2.7)
172 (61.0%)
0 (0.0%)
Tree Building Tree Building
175
240 (avg. 1.4)
63 (36.0%)
1 (0.6%)
Zipper Zipper
156
271 (avg. 1.7)
58 (37.2%)
0 (0.0%)
Circular Buffer Circular Buffer
306
546 (avg. 1.8)
158 (51.6%)
0 (0.0%)
Diffie-Hellman Diffie-Hellman
210
292 (avg. 1.4)
104 (49.5%)
1 (0.5%)
Hangman Hangman
156
317 (avg. 2.0)
28 (17.9%)
4 (2.6%)
List Ops List Ops
256
541 (avg. 2.1)
126 (49.2%)
2 (0.8%)
Custom Set Custom Set
278
497 (avg. 1.8)
117 (42.1%)
1 (0.4%)
Satellite Satellite
152
331 (avg. 2.2)
55 (36.2%)
1 (0.7%)
Leap Leap
2,692
4,023 (avg. 1.5)
2,115 (78.6%)
28 (1.0%)
Armstrong Numbers Armstrong Numbers
3,588
5,597 (avg. 1.6)
2,672 (74.5%)
81 (2.3%)
RNA Transcription RNA Transcription
4,819
9,796 (avg. 2.0)
3,976 (82.5%)
212 (4.4%)
Acronym Acronym
2,769
6,420 (avg. 2.3)
2,150 (77.6%)
65 (2.3%)
Pangram Pangram
3,869
6,898 (avg. 1.8)
3,183 (82.3%)
153 (4.0%)
Space Age Space Age
2,992
4,453 (avg. 1.5)
2,282 (76.3%)
52 (1.7%)
Connect Connect
202
937 (avg. 4.6)
97 (48.0%)
4 (2.0%)
SGF Parsing SGF Parsing
35
346 (avg. 9.9)
16 (45.7%)
2 (5.7%)
POV POV
23
20 (avg. 0.9)
7 (30.4%)
0 (0.0%)
Ledger Ledger
43
36 (avg. 0.8)
14 (32.6%)
2 (4.7%)
High Scores High Scores
158
1,203 (avg. 7.6)
127 (80.4%)
2 (1.3%)
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
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DOT DSL DOT DSL
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Killer Sudoku Helper Killer Sudoku Helper
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Lens Person Lens Person
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PaaS I/O PaaS I/O
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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
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Square Root Square Root
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State of Tic-Tac-Toe State of Tic-Tac-Toe
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