Java - Convert ArrayList Examples in Collection Framework

Java ArrayList Examples - Conversions

Here we will see some java array list examples e.g How to covert LinkedList to ArrayList, How to convert ArrayList to String array, How to convert Vector to ArrayList, etc. This is article is also very important from core java interview point of view.

So let's start without any delay.

(1) Java Convert - LinkedList to ArrayList Example

This is the simple example of java LinkedList to ArrayList conversion.

import java.util.*;

class Simple1

{

public static void main(String args[])

{
//declaring LinkedList

LinkedList<String> ll = new LinkedList<String>();

ll.add("nice");//adding elements

ll.add("good");

ll.add("bad");

ll.add("better");

ll.add("nice");

ll.add("awesome");

//declaring ArrayList 

ArrayList<String> al = new ArrayList<String>(ll);

//Traversing elements by using Iterator interface

Iterator it = al.iterator();

while(it.hasNext())

{

System.out.println(it.next());

}

}

}

Output: nice
             good
             bad
             better
             nice
             awesome

(2) Java - Convert ArrayList to String array

This is the simple example of ArrayList to String array conversion.

import java.util.*;

class Simple2

{

public static void main(String args[])

{

//declaring ArrayList Object

List<String> al = new ArrayList<String>();

al.add("india");//adding some elements to the array list

al.add("america");

al.add("england");

al.add("sri lanka");

al.add("india");

//creating String array

String[] str = new String[al.size()];

al.toArray(str);//using toArray() method for conversion

//traversing the elements one by one using for each loop

for(String s : str)

{

System.out.println(s);

}

}

}

Output: india
             america
             england
             sri lanka
             india

(3) Java - Convert Vector to ArrayList

This is another simple example of Vector class conversion to ArrayList class in java collection framework.

import java.util.*;
class Simple3
{
public static void main(String args[])
{
//declaring Vector object
Vector<String> v = new Vector<String>();
v.add("blue");//adding some values to the Vector
v.add("blue");
v.add("yellow");
v.add("green");
v.add("pink");
v.add("white");

//declaring ArrayList Object and pass Vector Object 
ArrayList<String> al = new ArrayList<String>(v);
//traversing elements
for(String s : al)
{
System.out.println(s);
}
}
} 

Output: blue
             blue
             yellow
             green
             pink
             white

(4) Java - Convert Array to ArrayList

This is another simple example of Array to ArrayList conversion in java.

import java.util.*;

class Simple4

{

public static void main(String args[])

{

//declaring ArrayList

ArrayList<String> al = new ArrayList<String>();
//declaring and initializing String array

String str[] = {"priya", "suman", "simran", "siya"};

for(int i = 0; i<str.lenght; i++)

{
al.add(str[i]);//adding array's elements to the arraylist

}

for(String s : al)

{

System.out.println(s);

}

}

}

Output: priya

             suman

             simran

             siya

(5) Java - Convert HashSet to ArrayList

In this example we will convert HashSet class into ArrayList in java.

import java.util.*;
class Simple5
{
public static void main(String args[])
{
//declaring HashSet
Set<String> hs = new HashSet<String>();
hs.add("pink");//adding some elements to the hash set
hs.add("red");
hs.add("blue");
hs.add("black");

//It will print hash set elements

System.out.println("HashSet Elements "+hs);

//declaring ArrayList
ArrayList<String> al = new ArrayList<String>(hs);

//It will array list elements in java
System.out.println("ArrayList Elements "+al);
}
}

Output: HashSet Elements [red, pink, blue, black]
             ArrayList Elements [red, pink, blue, black]

Above all the examples like linkedlist to arraylist, arraylist to string array, hashset to arraylist, vector to arraylist and array to arraylist are quite useful for any core java programming interview questions.

You can check this article to learn ArrayList class in detail.

Read More:

Java Collection Framework Interview Questions.
Difference Between ArrayList and Vector in Java.
Difference Between ArrayList and LinkedList in Java.
Difference Between HashSet and HashMap in Java.