Apex Developer Guide

Apex Developer Guide
Release Notes
Getting Started with Apex
Writing Apex
Data Types and Variables
Control Flow Statements
Classes, Objects, and Interfaces
Classes
Interfaces
Keywords
Using the final Keyword
Using the instanceof Keyword
Using the super Keyword
Using the this Keyword
Using the transient Keyword
Using the with sharing, without sharing, and inherited sharing Keywords
Annotations
Classes and Casting
Differences Between Apex Classes and Java Classes
Class Definition Creation
Namespace Prefix
Apex Code Versions
Lists of Custom Types and Sorting
Using Custom Types in Map Keys and Sets
Working with Data in Apex
Running Apex
Debugging, Testing, and Deploying Apex
Apex Reference
Appendices
PDF

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Using the instanceof Keyword

If you need to verify at run time whether an object is actually an instance of a particular class, use the instanceof keyword. The instanceof keyword can only be used to verify if the target type in the expression on the right of the keyword is a viable alternative for the declared type of the expression on the left.

You could add the following check to the Report class in the classes and casting example before you cast the item back into a CustomReport object.
1if (Reports.get(0) instanceof CustomReport) {
2    // Can safely cast it back to a custom report object
3   CustomReport c = (CustomReport) Reports.get(0);
4   } else {
5   // Do something with the non-custom-report.
6}

Implementation Considerations

Keep these considerations in mind while using the instanceof keyword.

  • If the declared type on the left of the expression using the instanceof keyword is always an instance of the target type, compilation fails. An example expression that’s always true and therefore causes a compilation error.
    1Account acc = new Account();
2if(acc instanceOf Account) {
3     //condition is always true since an instance of Account is always an instance of Account
4}
  • When you perform instanceof checks, implicit type casting from String to ID can result in unexpected behavior if the String meets the requirements to be cast to an ID.

Versioned Behavior Changes

In API version 60.0 and later, if a List data type implements the Iterable data type, compilation fails. An example instanceof expression that causes a compilation error.

1public class BaseClass {}
2public class SubClass extends BaseClass {}
3
4List<SubClass> subClasses = new List<SubClass>();
5if(subClasses instanceof Iterable<BaseClass>) {
6    //condition is always true since an instance of SubClass is always an instance of BaseClass
7}

In API version 32.0 and later, instanceof returns false if the left operand is a null object. In API version 31.0 and earlier, instanceof returns true in this case. For example, the code sample returns false in API version 32.0 and later.

1Object o = null;
2Boolean result = o instanceof Account;
3System.assertEquals(false, result);