Groovy: Operator Overloading

Groovy support operator overloading. For example, I am going to show, how to override + and – operators to the custom class Box.

HelloWorld.groovy

class Box{
 int width
 int height
 
 Box(int width, int height){
  this.width = width
  this.height = height
 }
 
 Box plus(Box other) {                     
        int newWidth = this.width + other.width
  int newHeight = this.height + other.height
  return new Box(newWidth, newHeight)
    }
 
 Box minus(Box other){
        int newWidth = this.width - other.width
  int newHeight = this.height - other.height
  return new Box(newWidth, newHeight) 
 }
 
 void aboutMe(){
  println "height : ${this.height}, width : ${this.width}"
 }
}

Box box1 = new Box(100, 120)
Box box2 = new Box(50, 60)

Box newBox1 = box1 + box2
Box newBox2 = box1 - box2

box1.aboutMe()
box2.aboutMe()
newBox1.aboutMe()
newBox2.aboutMe()

Output

height : 120, width : 100
height : 60, width : 50
height : 180, width : 150
height : 60, width : 50

You can even overload the plus and minus methods to support different data types.

         Box plus(int num){

                  int newWidth = this.width + num

                  int newHeight = this.height + num

                  return new Box(newWidth, newHeight)

         }

HelloWorld.groovy

class Box{
 int width
 int height
 
 Box(int width, int height){
  this.width = width
  this.height = height
 }
 
 Box plus(Box other) {                     
        int newWidth = this.width + other.width
  int newHeight = this.height + other.height
  return new Box(newWidth, newHeight)
    }
 
 Box plus(int num){
  int newWidth = this.width + num
  int newHeight = this.height + num
  return new Box(newWidth, newHeight)
 }
 
 Box minus(Box other){
        int newWidth = this.width - other.width
  int newHeight = this.height - other.height
  return new Box(newWidth, newHeight) 
 }
 
 void aboutMe(){
  println "height : ${this.height}, width : ${this.width}"
 }
}

Box box1 = new Box(100, 120)
box1 = box1 + 11
box1.aboutMe()

Output

height : 131, width : 111

Below table summarize the operators and corresponding methods supported by Groovy.

Operator	Method
+	a.plus(b)
-	a.minus(b)
*	a.multiply(b)
/	a.div(b)
%	a.mod(b)
**	a.power(b)
|	a.or(b)
&	a.and(b)
^	a.xor(b)
as	a.asType(b)
a()	a.call()
a[b]	a.getAt(b)
a[b] = c	a.putAt(b, c)
a in b	b.isCase(a)
<<	a.leftShift(b)
>>	a.rightShift(b)
>>>	a.rightShiftUnsigned(b)
++	a.next()
--	a.previous()
+a	a.positive()
-a	a.negative()
~a	a.bitwiseNegate()

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