K2J-Compat

Bringing Kotlin's scope functions and the safe call operator to Java

Description

Kotlin's scope functions (let, also, takeIf and takeUnless) and the safe call operator are now available to Java.

Programming language: Java

License: Apache License 2.0

Tags: Kotlin     Android     Java     Android-library     Compatibility     Let     Also    

Latest version: v1.0.1

README

K2J-Compat

Bringing some of the Kotlin goodness to java

Installation with Android Gradle

// Add K2J-Compat dependency
dependencies {
    implementation 'com.github.alexdochioiu:k2j-compat:1.0.1'
}

Usage

1. Kotlin's .let{ } as .let()

import static com.github.alexdochioiu.k2jcompat.K2JCompat.take;

final String number = take("[phone]")
                .let((it) -> "0" + it.substring(4)) // 077 1234 1234
                .let((it) -> it.replaceAll(" ", "")) // 07712341234
                .unwrap(); // unwraps the result to String

2. Kotlin's ?.let{ } as ._let()

import static com.github.alexdochioiu.k2jcompat.K2JCompat.take;

final String nullStr = null;
final String number = take(nullStr)
                ._let((it) -> it.replaceAll(" ", "")) // this code will not run as 'it' is null
                .unwrap(); // returns null

3. Kotlin's .also{ } as .also()

import static com.github.alexdochioiu.k2jcompat.K2JCompat.take;

StringBuilder builder = new StringBuilder();
take(builder).also((it) -> it.append("Hello World!"));

4. Kotlin's ?.also{ } as ._also()

import static com.github.alexdochioiu.k2jcompat.K2JCompat.take;

StringBuilder builder = null;
take(builder)._also((it) -> it.append("Hello World!"));
// Note: using 'also' instead of '_also' will cause a null pointer exception when trying to append

5. Kotlin's .takeIf{ } as .takeIf()

import static com.github.alexdochioiu.k2jcompat.K2JCompat.take;

String phoneNumber = "889944";
Integer number = take(phoneNumber)
                .takeIf((it) -> it.matches("[0-9]+"))
                ._let(Integer::parseInt)
                .unwrap();

6. Kotlin's ?.takeIf{ } as ._takeIf()

import static com.github.alexdochioiu.k2jcompat.K2JCompat.take;

String phoneNumber = null;
Integer number = take(phoneNumber)
                ._takeIf((it) -> it.matches("[0-9]+"))
                ._let(Integer::parseInt)
                .unwrap();

Note: If you use int instead of Integer NPE will be thrown as java will try to unbox a null Integer to int

7. Kotlin's .takeUnless{ } as .takeUnless()

Similar to takeIf but with inverted logic

8. Kotlin's ?.takeUnless{ } as ._takeUnless()

Similar to _takeIf but with inverted logic

Known Limitations

• Unlike Kotlin, Java has primitive data types which get boxed/unboxed automatically into objects when needed. However, NPE is thrown when Java tries to unbox a null Object to a primitive data type. This cannot be solved so a custom lint will be created to add a warning when using primitives are used.