Groovy - Map keySet() method

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Description

Groovy Map keySet() method obtain a Set of the keys in this Map.

Syntax

public Set keySet()

Parameters

NA

Return Value

Set of Keys.

Example - Getting Set of Keys from a Map of String and String

Following is an example of the usage of this method −

main.groovy

// define a map
def map = ["TopicName" : "Maps", "TopicDescription" : "Methods in Maps"] 

// get the set of keys
println(map.keySet())

Output

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

[TopicName, TopicDescription]

Example - Getting Set of Keys from a Map of Integer and String

Following is an example of the usage of this method −

main.groovy

// define a map
def map = [1 : "Apple", 2 : "Banana"] 

// get the set of keys
println(map.keySet())

Output

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

[1, 2]

Example - Getting Set of Keys from 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")] 

// get the set of keys
println(map.keySet())

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, 2]