Groovy - Map subMap(Collection keys) method

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Description

Groovy Map subMap(Collection keys) method returns a submap from current map based on the keys passed. Original map is unaffected.

Syntax

public Map subMap(Collection keys)

Parameters

Object[] − collection of keys

Return Value

A sub map containing given keys.

Example - Getting a Sub Map of String and String

Following is an example of the usage of this method −

main.groovy

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

// get a sub map based on keys
result = map.subMap(["A","B"])

// print sub map
print(result)

Output

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

[A:Apple, B:Banana]

Example - Getting a Sub Map of Integer and Integer

Following is an example of the usage of this method −

main.groovy

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

// get a sub map based on keys
result = map.subMap([1,2])

// print sub map
print(result)

Output

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

[1:11, 2:12]

Example - Getting a Sub Map of Integer and Object

Following is an example of the usage of this method −

main.groovy

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

// get a sub map based on keys
result = map.subMap([1,2])

// print sub map
print(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 ]]