Groovy - Map each(Closure closure) method

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Description

Groovy Map each(Closure closure) method allows a map to be iterated through using passed closure.

Syntax

public Map each(Closure closure)

Parameters

closure − 1 or 2 args closure to be applied on each entry of the map.

Return Value

Returns self.

Example - Iterating entries of a Map of String and String

Following is an example of the usage of this method −

main.groovy

// define a map
def map = ["A" : "Apple", "B" : "Banana", "C": "Carrot"] 

def result = ""
// iterate entries of map using 1 arg constructor
// and update result
map.each{entry -> result += entry}

println(result)

result = ""

// iterate entries of map using 2 args constructors
// and update result
map.each{key, value -> result += "$key=$value"}

println(result)

Output

When we run the above program, we will get the following result −

A=AppleB=BananaC=Carrot
A=AppleB=BananaC=Carrot

Example - Iterating entries of a Map of Integer and Integer

Following is an example of the usage of this method −

main.groovy

// define a map
def map = [1 : 11, 2 : 12, 3: 13] 

def result = ""
// iterate entries of map using 1 arg constructor
// and update result
map.each{entry -> result += entry}

println(result)

result = ""

// iterate entries of map using 2 args constructors
// and update result
map.each{key, value -> result += "$key=$value"}

println(result)

Output

When we run the above program, we will get the following result −

1=112=123=13
1=112=123=13

Example - Iterating entries of a Map of Integer and Object

Following is an example of the usage of this method −

main.groovy

// define a map
def map = [1 : new Student(1, "Julie"), 2 : new Student(2, "Robert"), 3: new Student(3,"Adam")] 

def result = ""
// iterate entries of map using 1 arg constructor
// and update result
map.each{entry -> result += entry}

println(result)

result = ""

// iterate entries of map using 2 args constructors
// and update result
map.each{key, value -> result += "$key=$value"}

println(result)

class Student{
   int rollNo
   String name

   Student(int rollNo, String name){
      this.rollNo = rollNo
      this.name = name
   }

   @Override
   public boolean equals(Object obj) {
      Student s = (Student)obj
      return this.rollNo == s.rollNo && this.name.equalsIgnoreCase(s.name)
   }
   
   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]"
   }
}

Output

When we run the above program, we will get the following result −

1=[ 1, Julie ]2=[ 2, Robert ]3=[ 3, Adam ]
1=[ 1, Julie ]2=[ 2, Robert ]3=[ 3, Adam ]