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kotlin-cookbook

README.md

Kotlin Cookbook code examples ⬆

Kotlin project Directory kotlin-cookbook\ contains Kotlin code examples from Ken Kousen's book "Koltin Cookbook" (O'Reilly, 2019).
It also includes several build scripts (batch files, Gradle scripts) for experimenting with Kotlin on a Windows machine.

Example 03-10 ― Customer class

Lazy loading can be implemented the hard way (with a private nullable property) or using a built-in lazy delegate function.

This example has the following directory structure :

> tree /f /a . | findstr /v /b [A-Z]
|   build.bat
|   build.gradle
|   gradle.properties
|   Makefile
|   pom.xml
\---src
    +---main
    |   \---kotlin
    |           Customer.kt
    \---test
        \---kotlin
                CustomerKtTest.kt

Command build.bat clean run compiles the source files Customer.kt and executes the generated Java class files :

> cd
K:\kotlin-cookbook\Example_03-10
 
> build clean run
Customer name: Fred

Command build -verbose test compiles the source file CustomerKtTest.kt and executes the implemented unit tests :

> build -verbose test
No action required ('src\main\kotlin\*.kt')
Compile 1 Kotlin test source files (JVM) to directory "target\test-classes"
Execute test CustomerKtTestKt
.
+-- JUnit Jupiter [OK]
| '-- CustomerKtTest [OK]
|   '-- load messages() [OK]
'-- JUnit Vintage [OK]

Test run finished after 85 ms
[         3 containers found      ]
[         0 containers skipped    ]
[         3 containers started    ]
[         0 containers aborted    ]
[         3 containers successful ]
[         0 containers failed     ]
[         1 tests found           ]
[         0 tests skipped         ]
[         1 tests started         ]
[         0 tests aborted         ]
[         1 tests successful      ]
[         0 tests failed          ]

Example 03-13 ― Overriding operator on Point

This example has the following directory structure :

> tree /f /a . | findstr /v /b [A-Z]
|   build.bat
|   build.gradle
|   gradle.properties
|   Makefile
|   pom.xml
\---src
    +---main
    |   \---kotlin
    |           PointMain.kt
    \---test
        \---kotlin
                PointMainKtTest.kt

Command build.bat clean run compiles the source files PointMain.kt and executes the generated Java class files:

> cd
K:\kotlin-cookbook\Example_03-13
 
> build clean run
Point(x=-10, y=-20)

Command build -verbose test compiles the source file PointMainKtTest.kt and executes the implemented unit tests.

> build -verbose test
No action required ('src\main\kotlin\*.kt')
Compile 1 Kotlin test source files (JVM) to directory "target\test-classes"
Execute test MainKtTest
.
+-- JUnit Jupiter [OK]
| '-- MainKtTest [OK]
|   '-- point with negative axes$main() [OK]
'-- JUnit Vintage [OK]

Test run finished after 70 ms
[         3 containers found      ]
[         0 containers skipped    ]
[         3 containers started    ]
[         0 containers aborted    ]
[         3 containers successful ]
[         0 containers failed     ]
[         1 tests found           ]
[         0 tests skipped         ]
[         1 tests started         ]
[         0 tests aborted         ]
[         1 tests successful      ]
[         0 tests failed          ]

Example 03-14 ― Extension functions on Complex

Command build.bat clean run compiles the source files ComplexOverloadOperators.kt and executes the generated Java class files:

> cd
K:\kotlin-cookbook\Example_03-14
 
> build clean run
x   = (1.0, 3.0)
y   = (2.0, 5.0)
x+y = (3.0, 8.0)
x*y = (-13.0, 11.0)

Command build.bat -verbose test compiles the source file ComplexOverloadOperatorsKtTest.kt and executes the implemented unit tests.

> build -verbose test
No action required ('src\main\kotlin\*.kt')
Compile 1 Kotlin test source files (JVM) to directory "target\test-classes"
Execute test ComplexOverloadOperatorsKtTest
.
+-- JUnit Jupiter [OK]
| '-- ComplexOverloadOperatorsKtTest [OK]
|   +-- Euler's formula$main() [OK]
|   +-- plus$main() [OK]
|   +-- negate$main() [OK]
|   '-- minus$main() [OK]
'-- JUnit Vintage [OK]

Test run finished after 99 ms
[         3 containers found      ]
[         0 containers skipped    ]
[         3 containers started    ]
[         0 containers aborted    ]
[         3 containers successful ]
[         0 containers failed     ]
[         4 tests found           ]
[         0 tests skipped         ]
[         4 tests started         ]
[         0 tests aborted         ]
[         4 tests successful      ]
[         0 tests failed          ]

Example 04-01 ― Summing integers by using fold

Command build.bat clean run compiles the source files FoldMain.kt and executes the generated Java class files:

> cd
K:\kotlin-cookbook\Example_04-01
 
> build clean run
nums = [1, 3, 5, 7]
sum(*nums) = 16

acc = 0, n = 1
acc = 1, n = 3
acc = 4, n = 5
acc = 9, n = 7
sumWithTrace(*nums) = 16

factorialFold(20) = 2432902008176640000

fibonacciFold(20) = 6765

Command build.bat -verbose test compiles the source file FoldMainKtTest.kt and executes the implemented unit tests.

> build -verbose test
No action required ('src\main\kotlin\*.kt')
Compile 1 Kotlin test source files (JVM) to directory "target\test-classes"
Execute test FoldMainKtTest
.
+-- JUnit Jupiter [OK]
| '-- FoldMainKtTest [OK]
|   '-- sum using fold$main() [OK]
'-- JUnit Vintage [OK]

Test run finished after 100 ms
[         3 containers found      ]
[         0 containers skipped    ]
[         3 containers started    ]
[         0 containers aborted    ]
[         3 containers successful ]
[         0 containers failed     ]
[         1 tests found           ]
[         0 tests skipped         ]
[         1 tests started         ]
[         0 tests aborted         ]
[         1 tests successful      ]
[         0 tests failed          ] build -verbose test

mics/January 2025 ▲