Groovy: Rules while evaluating the expressions

Groovy follow below rules while evaluating the expressions.

Non-Zero numbers are evaluated to true

HelloWorld.groovy

nonZeroNumber = 10
zeroNumber = 0

printInfo (nonZeroNumber)
printInfo (zeroNumber)

void printInfo(obj){
 if(obj){
  println "$obj evaluated to true"
 }else{
  println "$obj evaluated to false"
 }
}

Output

10 evaluated to true

0 evaluated to false

Non-null objects are evaluated to true

HelloWorld.groovy

obj1 = null
obj2 = "Hello"

printInfo (obj1)
printInfo (obj2)

void printInfo(obj){
 if(obj){
  println "$obj evaluated to true"
 }else{
  println "$obj evaluated to false"
 }
}

Output

null evaluated to false

Hello evaluated to true

Non-empty Strings, GStrings and CharSequences are coerced to true.

HelloWorld.groovy

emptyStr = ""
nonEmptyStr = "Hello World"

printInfo(emptyStr)
printInfo(nonEmptyStr)

void printInfo(data){
 if(data){
  println "$data is evaluated to true"
 }else{
  println "$data is evaluated to false" 
 }
}

Output

is evaluated to false

Hello World is evaluated to true

Non-empty Collections and arrays are evaluated to true.

HelloWorld.groovy

emptyArray = []
emptyMap = [:]

array = [1, 2, 3]
map = ['color':'Blue', 'shape':'Circle']

printInfo(emptyArray)
printInfo(emptyMap)
printInfo(array)
printInfo(map)

void printInfo(data){
 if(data){
  println "$data is evaluated to true"
 }else{
  println "$data is evaluated to false" 
 }
}

Output

[] is evaluated to false

[:] is evaluated to false

[1, 2, 3] is evaluated to true

[color:Blue, shape:Circle] is evaluated to true

Evaluate to true, if the matcher has atleast one match

HelloWorld.groovy

def text = "aaaab"

if (text =~ /a*b/){
 println 'Evaluate to true'
}else{
 println "Evaluated to false"
}  

Output

Evaluate to true

Iterators and Enumerators with further elements are evaluated as true

HelloWorld.groovy

Iterator iter1 = [0].iterator()
Iterator iter2 = [].iterator()

Vector vector1 = [0] as Vector
Enumeration enumerator1 = vector1.elements()

Vector vector2 = [] as Vector
Enumeration enumerator2 = vector2.elements()

printInfo(iter1, "iter1")
printInfo(iter2, "iter2")
printInfo(enumerator1, "enumerator1")
printInfo(enumerator2, "enumerator2")

void printInfo(obj, message){
 if(obj){
  println "$message evaluated to true"
 }else{
  println "$message evaluated to false"
 }
}

Output

iter1 evaluated to true

iter2 evaluated to false

enumerator1 evaluated to true

enumerator2 evaluated to false

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