Sample Code:


Visualforce page:

1. <apex:page controller=“Sample”>  
2.       
3.     <apex:form >  
4.       
5.         <apex:pageBlock >  
6.           
7.             <apex:pageMessages />  
8.           
9.             Testing Page Message  
10.               
11.             <apex:pageBlockButtons location=“bottom”>  
12.               
13.                 <apex:commandButton value=“Call” action=“{!check}”/>  
14.                   
15.             </apex:pageBlockButtons>  
16.               
17.         </apex:pageBlock>  
18.           
19.     </apex:form>  
20.       
21. </apex:page>  

Apex Class:

1. public class Sample {  
2.   
3.     public Sample() {  
4.           
5.     }  
6.       
7.     public void check() {  
8.       
9.         ApexPages.addmessage(new ApexPages.message(ApexPages.severity.CONFIRM,‘Check button is clicked’));  
10.           
11.     }  
12.       
13. }  

Output: