Groovy - Map asUnmodifiable() method

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Description

Groovy Map asUnmodifiable() method returns an unmodifiable copy of the current map.

Syntax

public Map asUnmodifiable()

Parameters

NA

Return Value

an unmodifiable copy of the map

Example - Getting Immutable 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 unmodifiableMap = map.asUnmodifiable()

try {
   // try to add a new value to the map
   unmodifiableMap.put("M","Mango")
}catch(UnsupportedOperationException e){
    println("Entry cannot be added.")
} 

try {
   // try to uodate value of the map
   unmodifiableMap.put("B","Mango")
}catch(UnsupportedOperationException e){
    println("Map cannot be modified.")
} 

Output

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

Entry cannot be added.
Map cannot be modified.

Example - Getting immutable 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: 6] 

def unmodifiableMap = map.asUnmodifiable()

try {
   // try to add a new value to the map
   unmodifiableMap.put(4,14)
}catch(UnsupportedOperationException e){
    println("Entry cannot be added.")
} 

try {
   // try to uodate value of the map
   unmodifiableMap.put(3,13)
}catch(UnsupportedOperationException e){
    println("Map cannot be modified.")
} 

Output

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

Entry cannot be added.
Map cannot be modified.

Example - Getting immutable of 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")] 

def unmodifiableMap = map.asUnmodifiable()

try {
   // try to add a new value to the map
   unmodifiableMap.put(3,new Student(3, "Adam"))
}catch(UnsupportedOperationException e){
    println("Entry cannot be added.")
} 

try {
   // try to uodate value of the map
   unmodifiableMap.put(2,new Student(3, "Adam"))
}catch(UnsupportedOperationException e){
    println("Map cannot be modified.")
} 

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 −

Entry cannot be added.
Map cannot be modified.