Array To ArrayList And ArrayList To Array In Java With Examples

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Array and ArrayList are two most frequently used data types in java. Array is old derived type which can hold primitive types as well as objects where as ArrayList is a part of Java Collection Framework which holds only objects. One more difference is that array is of fixed size. You can’t change its size once it is created. But, ArrayList is re-sizable. It grows and shrinks as you insert or delete the elements. While coding, you often need to perform the conversion between these two i.e Array to ArrayList and ArrayList to Array. In this post, we will see how to convert Array to ArrayList and ArrayList to Array in java with some simple examples.

Array To ArrayList In Java :

a) Using Arrays.asList() Method :

import java.util.ArrayList;
import java.util.Arrays;

public class ArrayToArrayListExample 
{  	
	public static void main(String[] args) 
	{	
		String[] array = new String[] {"ANDROID", "JSP", "JAVA", "STRUTS", "HADOOP", "JSF"};
		
		ArrayList<String> list = new ArrayList<String>(Arrays.asList(array));
		
		System.out.println(list);
	}	
}

Output :

[ANDROID, JSP, JAVA, STRUTS, HADOOP, JSF]

b) Using Collections.addAll() Method

import java.util.ArrayList;
import java.util.Collections;

public class ArrayToArrayListExample 
{  	
	public static void main(String[] args) 
	{	
		String[] array = new String[] {"ANDROID", "JSP", "JAVA", "STRUTS", "HADOOP", "JSF"};
		
		ArrayList<String> list = new ArrayList<String>();
		
		Collections.addAll(list, array);
		
		System.out.println(list);
	}	
}

Output :

[ANDROID, JSP, JAVA, STRUTS, HADOOP, JSF]

c) Using ArrayList.addAll() Method :

import java.util.ArrayList;
import java.util.Arrays;

public class ArrayToArrayListExample 
{  	
	public static void main(String[] args) 
	{	
		String[] array = new String[] {"ANDROID", "JSP", "JAVA", "STRUTS", "HADOOP", "JSF"};
		
		ArrayList<String> list = new ArrayList<String>();
		
		list.addAll(Arrays.asList(array));
		
		System.out.println(list);
	}	
}

Output :

[ANDROID, JSP, JAVA, STRUTS, HADOOP, JSF]

d) Using Streams from Java 8

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class ArrayToArrayListExample 
{  	
	public static void main(String[] args) 
	{	
		String[] array = new String[] {"ANDROID", "JSP", "JAVA", "STRUTS", "HADOOP", "JSF"};
		
		List<Object> list = Arrays.stream(array).collect(Collectors.toList());
		
		System.out.println(list);
	}	
}

Output :

[ANDROID, JSP, JAVA, STRUTS, HADOOP, JSF]

ArrayList To Array In Java :

import java.util.ArrayList;

public class ArrayListToArrayExample 
{  	
	public static void main(String[] args) 
	{	
		ArrayList<String> list = new ArrayList<String>();
		
		list.add("JAVA");
		
		list.add("JSP");
		
		list.add("ANDROID");
		
		list.add("STRUTS");
		
		list.add("HADOOP");
		
		list.add("JSF");
		
		String[] array = new String[list.size()]; 
		
		list.toArray(array);
		
		for (String string : array)
		{
			System.out.println(string);
		}
	}	
}

Output :

JAVA
JSP
ANDROID
STRUTS
HADOOP
JSF

Also Read :

String To Integer And Integer To String In Java

HashMap To ArrayList In Java

Decimal to binary, octal and hexadecimal in java

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