Print a Collection in Java

In this article, we will understand how to print a collection in Java. The Collection is a framework that provides architecture to store and manipulate the group of objects. Java Collections can achieve all the operations that you perform on a data such as searching, sorting, insertion, manipulation, and deletion.

Problem Statement

Write a program in Java to print a Collection. Below is a demonstration of the same ?

Input 

Run the program

Output

The Elements of the collection are:
Language : Java | Language_id : 101
Language : Scala | Language_id : 102
Language : Python | Language_id : 103
Language : Mysql | Language_id : 104

Different approaches to print a collection in Java

Following are the different approaches to print a collection in Java ?

• Using the main method
• Using encapsulation

Using the main method

Following are the steps to print a collection in Java ?

• First we will import all the necessary classes from java.util package.
• Intialize the public class which is the Demo class.
• Create a Demo class with attributes name (String) and id (int) and initialize the Demo class attributes using a constructor.
• And use the toString() method to print name and id in a formatted way.
• Inside the main method, create an ArrayList of Demo objects.
  
• Add several Demo objects to the ArrayList.
  
• Use a for-each loop to iterate through and print each element of the ArrayList.
  

Example 

Here, we bind all the operations together under the ?main' method ?

import java.util.*;
public class Demo {
   String name;
   int id;
   Demo(String s, int n){
      name = s;
      id = n;
   }
   public String toString(){
      return "Language : " + name + " | Language_id : " + id;
   }
   public static void main(String[] args){
      ArrayList<Demo> input_array = new ArrayList<Demo>();
      Demo object_1 = new Demo("Java", 101);
      Demo object_2 = new Demo ("Scala", 102);
      Demo object_3 = new Demo("Python", 103);
      Demo object_4 = new Demo("Mysql", 104);
      input_array.add(object_1);
      input_array.add(object_2);
      input_array.add(object_3);
      input_array.add(object_4);
      System.out.println("The Elements of the collection are: ");
      for (Demo element : input_array)
         System.out.println(element);
   }
}

Output

The Elements of the collection are:
Language : Java | Language_id : 101
Language : Scala | Language_id : 102
Language : Python | Language_id : 103
Language : Mysql | Language_id : 104

Using encapsulation

Following are the steps to print a collection in Java using encapsulation ?

• Import necessary classes from java.util package.
• Create a Demo class with attributes name (String) and id (int).
• Initialize the Demo class attributes using a constructor.
• And we will use toString() method to print name and id in a formatted way.
• Define a static method named print to encapsulate the logic of printing the collection.
• Inside the main method, create an ArrayList of Demo objects.
• Add several Demo objects to the ArrayList.
  
• Call the print method to print all elements of the collection.
  

Example 

Here, we encapsulate the operations into functions exhibiting object-oriented programming ?

import java.util.*;
public class Demo {
   String name;
   int id;
   Demo(String s, int n){
      name = s;
      id = n;
   }
   public String toString(){
      return "Language : " + name + " | Language_id : " + id;
   }
   static void print(ArrayList<Demo> input_array){
      System.out.println("The Elements of the collection are: ");
      for (Demo element : input_array)
         System.out.println(element);
   }
   public static void main(String[] args){
      ArrayList<Demo> input_array = new ArrayList<Demo>();
      Demo object_1 = new Demo("Java", 101);
      Demo object_2 = new Demo("Scala", 102);
      Demo object_3 = new Demo("Python", 103);
      Demo object_4 = new Demo("Mysql", 104);
      input_array.add(object_1);
      input_array.add(object_2);
      input_array.add(object_3);
      input_array.add(object_4);
      print(input_array);
   }
}

Output

The Elements of the collection are:
Language : Java | Language_id : 101
Language : Scala | Language_id : 102
Language : Python | Language_id : 103
Language : Mysql | Language_id : 104