Apex Arrays – Example to display Array of strings

Apex Arrays and Lists

An Apex array stores an ordered collection of elements of the same data type. Each element is identified by a zero-based index, so the first element is at index 0. In Apex, array notation and the List collection type are interchangeable; for example, String[] and List<String> describe the same kind of collection.

Apex Array Declaration Syntax

The following legacy snippet illustrates an attempted declaration. The corrected Apex forms are shown immediately below it.

<String> [] arrayOfProducts = new List<String>();

String[] arrayOfProducts = new List<String>();
List<String> productList = new List<String>();

Both declarations create an empty list of strings. Use either notation consistently within a class. The List<String> form is often clearer when working with collection methods such as add(), size(), and contains().

Dynamic Apex Array Declaration

Datatype[] arrayname =new DataType[size];

For Apex code, initialize an empty collection and add values as required. Apex lists grow dynamically, so a fixed capacity normally does not need to be declared.

String[] names = new String[]();
names.add('Malli');
names.add('Adarsh');

Static Apex Array Initialization

DataType[] arrayname =new DataType[] {20,40};

A static initializer supplies the elements when the collection is created. The declared element type must match the values in the initializer.

String[] names = new String[] {'Malli', 'Adarsh', 'Kiran'};
Integer[] scores = new Integer[] {20, 40};

Apex Array Notation Compared with List Collections

Apex does not treat array notation as a separate fixed-size collection. An Apex array is a list written with bracket notation. Both forms are ordered, indexed, dynamically sized, and restricted to the declared element type.

Feature	Array notation	List notation
Example	String[] names	List<String> names
Element type	String only	String only
Indexing	Zero-based	Zero-based
Size	Can grow or shrink	Can grow or shrink
Collection methods	List methods are available	List methods are available

Accessing and Printing an Apex Array of Strings

Use an index to read or replace one element. Check the collection size before accessing an index because an index outside the valid range causes a runtime exception. To inspect the complete array while developing, pass it to System.debug().

String[] names = new String[] {'Malli', 'Adarsh', 'Kiran'};

System.debug(names[0]);
System.debug(names);

for (String currentName : names) {
    System.debug(currentName);
}

The first debug statement prints the element at index 0. The enhanced for loop processes every string without requiring a numeric index.

Useful Apex List Methods for String Arrays

Operation	Apex example	Purpose
Add an element	names.add('Ravi');	Appends a string to the list.
Read an element	names.get(0)	Returns the value at the specified index.
Replace an element	names.set(0, 'Anita');	Replaces the value at an existing index.
Count elements	names.size()	Returns the current number of elements.
Check for a value	names.contains('Ravi')	Tests whether the list contains the supplied string.
Remove an element	names.remove(0)	Removes the element at the specified index.
Clear the list	names.clear()	Removes all elements.

Apex Controller for Displaying a String Array

The following example exposes an array of strings through an Apex controller and displays the values in a Visualforce pageBlockTable. To create the controller in the Developer Console, select File → New → Apex Class, enter ArrayExample as the class name, and save it.

• Enter the Apex class name to create new Apex Class.

ArrayExample Apex Class Code

Public class ArrayExample {
    Public String[] myval{set;get;}
    Public String name{get;set;}
    Public ArrayExample() {
        name = 'Prasanth';
        myval = new String[] {'Malli','Adarsh','kiran'};
    }
}

The constructor initializes myval with three strings. The public properties make the array and the name value available to the Visualforce page through their generated accessors.

Visualforce Page for the Apex String Array

The Visualforce page assigns the controller’s myval property to the table’s value attribute. During each iteration, the variable a represents one string in the array. The column renders that current value.

<apex:page controller="ArrayExample" >
    <apex:form>
        <apex:pageBlock>
            <apex:pageBlockTable value="{!myval}" var="a">
                <apex:column value="{!a}"/>
            </apex:pageBlockTable>
            <apex:outputLabel>{!name}</apex:outputLabel>
        </apex:pageBlock>
    </apex:form>    
</apex:page>

Output of the Apex Array Example

The page renders each value from myval as a separate table row and displays the value of name below the table.

Apex String Array Troubleshooting

• Invalid index: An array containing three elements has valid indexes from 0 through 2.
• Null collection: Declare and initialize the list before calling methods such as add().
• Type mismatch: A String[] accepts strings, not values of unrelated Apex types.
• Missing Visualforce access: Expose controller data through a public property or getter that the page can evaluate.
• Unexpected table output: Confirm that the table’s value references the array property and its var name matches the expression used by the column.

Apex Array Example QA Checklist

• Confirm that every array value matches the declared Apex element type.
• Verify that indexed access starts at zero and remains below size().
• Test the controller with an empty array as well as a populated array.
• Check that the Visualforce page references the correct controller property and iteration variable.
• Review debug logs to confirm the array contains the expected strings before the page renders.

Frequently Asked Questions About Apex Arrays

How do you create a list of strings in Apex?

Declare it as List<String> names = new List<String>();. You can also use the equivalent array notation, String[] names = new String[]();.

How do you declare an array with values in Apex?

Use an initializer such as String[] names = new String[] {'Malli', 'Adarsh', 'Kiran'};. The values must be compatible with the declared element type.

How do you print an Apex array of strings?

Use System.debug(names) to write the collection to a debug log. To process or print one value at a time, iterate over the array with a for loop.

Are Apex arrays fixed in size?

No. Apex array notation represents a List, which can grow when elements are added and shrink when elements are removed.

What is the difference between an Apex List and a Set?

A List is ordered, supports zero-based indexing, and can contain duplicate values. A Set stores unique values and does not provide indexed access.