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Java Operator Overloading

Java-OO is a modular extension (plugin) to Java compilers and IDEs for (Scala-like) Operator Overloading support. Works with standard JavaC compiler, Netbeans IDE, Eclipse IDE, IntelliJ IDEA IDE and any build tools.

Example (see other examples at examples/ dir):

import java.math.*;
import java.util.*;
public class Test {
  public static void main(String[] args) {
    BigInteger a = BigInteger.valueOf(1), // without OO
               b = 2, // with OO

    c1 = a.negate().add(b.multiply(b)).add(b.divide(a)), // without OO
    c2 = -a + b*b + b/a; // with OO

    if (c1.compareTo(c2)<0 || c1.compareTo(c2)>0) // without OO
      System.out.println("impossible");
    if (c1<c2 || c1>c2) // with OO
      System.out.println("impossible");

    HashMap<String, String> map = new HashMap<>();
    if (!map.containsKey("qwe")) map.put("qwe", map.get("asd")); // without OO
    if (map["qwe"]==null) map["qwe"] = map["asd"]; // with OO
  }
}

Versions

JavaC/Netbeans: 0.5
JavaC8:         0.5
Eclipse:        0.5
IntelliJ IDEA:  0.7

Note plugin versions are independent. If version for X > version for Y then it doesn't mean Y is behind feature wise.

News

16 Nov 2019. IntelliJ IDEA plugin v0.7 released with support of IDEA 2019.2+.

20 May 2017. IntelliJ IDEA plugin v0.6 released with support of IDEA 2017.

14 July 2016. As a workaround Eclipse plugin works fine on Eclipse 4.4+ if you install Scala IDE plugin first.

2 Feb 2016. IntelliJ IDEA plugin v0.5 released with support of IDEA 15. Requires Java8 to run the plugin.

10 April 2015. IntelliJ IDEA plugin v0.4.1 released with support of IDEA 14.1.

27 January 2015. Eclipse-oo-plugin version 0.5 released with support of reverse binary operator overload.

2 December 2014. New feature: Reverse binary operator overload via operatorRev methods.
Plugin versions updated:
JavaC7 & JavaC8: 0.5
IntelliJ IDEA: 0.4. Support of IDEA 14

31 May 2014. Javac8 plugin version 0.1.1 released. Removed runtime depencendy on nbjavac.

24 May 2014. IntelliJ IDEA plugin v0.3.1 released. Bugfixes for IDEA 13 Ultimate and for type resolution for binary expressions with primitives.

30 April 2014. IJPLA published a paper about Java-OO.

3 Feb 2014. New JavaC8 plugin version 0.1 for JDK8 was released. It has the same features as JavaC plugin for JDK7 but doesn't work in Netbeans yet.

12 Jan 2014. JavaC plugin version 0.4 and Eclipse plugin version 0.4 released. Now operator overloading perform autoboxing/autounboxing primitive to/from wrapper types where appropriate. Fixed javac plugin bug with index-set OO.

3 Jan 2014. JavaC plugin version 0.3 released. Fixed #10 javac: binary operator adds erroneous cast on 1st operand.

8 Sep 2013. Eclipse plugin version 0.3 released. Removed copypasta from Eclipse Compiler. Plugin should be more steady agains compiler changes.

14 May 2013. IntelliJ IDEA IDE plugin v0.2.1 with IDEA Ultimate Edition support.

17 Apr 2013. IntelliJ IDEA IDE plugin v0.2.

26 Nov 2012. Version 0.2 released. New feature: Assignment operator overloading via static #valueOf method.

Installation

javac, ant, etc

Just add to classpath: javac8-oo-plugin.jar for JDK8 or javac-oo-plugin.jar for JDK7.

javac -cp javac8-oo-plugin.jar <sources>

Demo at examples/compile.sh

Eclipse IDE update site

Click in menu: Help - Install New Software. Enter in Work with field:

http://amelentev.github.io/eclipse.jdt-oo-site/

Tested on Eclipse Standard 4.3.2. Should work with older versions too.
To work on 4.4+ you need to install Scala IDE plugin (or similar plugin with Equanox weaving). You can find it in Help -> Eclipse Marketplace. This is workaround until normal solution will be found. Tested on 4.4 and 4.6.

Netbeans IDE

  1. Add javac-oo-plugin.jar as compile or processor library to Netbeans.
  2. Enable "Annotation Processing in Editor": Project Properties -> Build -> Compiling.

Tested on 7.2.1

IntelliJ IDEA IDE

  1. Install Java Operator Overloading support plugin: File -> Settings -> Plugins -> Browse repositories. Mirror: idea-oo-plugin.jar)
    For Maven projects installation is done. IDEA should setup everything according to pom.xml.
    For other project types:
  2. Add javac8-oo-plugin.jar as compile or processor library.
  3. Enable Annotation Processing: Menu File -> Settings -> Compiler -> Annotation Processing -> Enable annotation processing
  4. Make sure you use javac compiler in Settings -> Java Compiler -> Use compiler.
    Tested on IDEA 2019.2.4 Ultimate & Community editions. You can use earlier plugin versions for older IDEA releases.

Android project in IDEA 12

Add javac-oo-plugin.jar to File - Settings - Compiler - Annotation Processors - Processor path

Android Studio (IDEA 13) / Gradle

add to build.gradle:

repositories {
	maven { url 'http://amelentev.github.io/mvnrepo/' }
}
dependencies {
	compile 'java-oo:javac-oo-plugin:0.5'
}

Maven

Look at javac-oo-mvndemo/pom.xml

Details

Read the paper to learn more. Supported operators (operator to method name map):

binary:

| OPERATOR | METHOD NAME|
-------------------------
| +        | add        |
| -        | subtract   |
| *        | multiply   |
| /        | divide     |
| %        | remainder  |
| &        | and        |
| |        | or         |
| ^        | xor        |
| <<       | shiftLeft  |
| >>       | shiftRight |

If left operand has no such method then the plugin will try to use 'reverse' method <methodName>Rev on right operand. So 2*a will be transformed to a.multiplyRev(2) if a has such method.

unary:

| -        | negate     |
| ~        | not        |

comparison:

| <, <=, >, >= | compareTo	| example: `a < b` <=> `a.compareTo(b)<0`
`==` and `!=` are not overloadable because it will break things

index:

| []  | get       | `v = lst[i]` <=> `v = lst.get(i)`
| []= | set, put  | `map[s] = v` <=> `map.put(s,v)`,  `lst[i] = v` <=> `lst.set(i,v)`

assignment:

| var = expr | var = VarClass.valueOf(expr) |

if expr is not assignable to var and var is an instance of VarClass and expr has type ExprType and there are static method VarClass#valueOf(ExprType)
then var = expr is transformed to var = VarClass.valueOf(expr). example:
BigInteger a = 1 is transformed to BigInteger a = BigInteger.valueOf(1)

These methods exists in many java classes (example: BigInteger, BigDecimal) so you can use operators on them "out of the box". Or you can add these methods to your classes to use OO (see examples/Vector.java).

Subprojects / Implementation details

Publications

"Java Modular Extension for Operator Overloading", IJPLA, April 2014.