Groovy - List toUnique() method

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Description

Groovy List toUnique() method returns the list without any duplicate while duplicates are removed as per the natural ordering of the elements.

Syntax

public List toUnique()

Parameters

NA

Return Value

A list of unique elements of the list.

Example - Getting Unique elements from a List of Integers

Following is an example of the usage of this method −

main.groovy

def lst = [11, 12, 13, 10, 15, 11, 10, 12, 15]

// getting list of unique elements
uniqueList = lst.toUnique()
println(uniqueList)

Output

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

[11, 12, 13, 10, 15]

Example - Getting Unique elements from a List of Strings

Following is an example of the usage of this method −

main.groovy

def lst = ["Apple","Mango","Orange","Papaya","Apple", "Apple"]

// getting list of unique elements
uniqueList = lst.toUnique()
println(uniqueList)

Output

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

[Apple, Mango, Orange, Papaya]

Example - Getting Unique elements from a List of Objects

Following is an example of the usage of this method −

main.groovy

def lst = [new Student(1, "Julie"),new Student(2, "Robert"),new Student(1, "Julie")]

// getting list of unique elements
uniqueList = lst.toUnique()
println(uniqueList)

class Student implements Comparable {
   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 + " ]";
   }
   
   public int compareTo(Object obj){
      Student s = (Student)obj;
      return this.rollNo - s.rollNo   
   }
}

Output

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

[[ 1, Julie ], [ 2, Robert ]]