Whitelist your Salesforce base URL in Remote Sites.

Step 1: Copy the Salesforce base URL. For example: “https://na40.salesforce.com/”.
Step 2: Go to Setup > Security Controls > Remote Site Settings .
Step 3: Click “New Remote Site” button. Enter the related Information and Save.

Apex controller code:

public with sharing class AccountRest {
    
    /**
	 * Webkul Software.
	 *
	 * @category  Webkul
	 * @author    Webkul
	 * @copyright Copyright (c) 2010-2016 Webkul Software Private Limited (https://webkul.com)
	 * @license   https://store.webkul.com/license.html
	**/
    
    public list<account> acc{get{
    
    	//Define http Request 
    	//append your Query to the base url
    	HttpRequest req = new HttpRequest();
        req.setEndpoint('https://'+URL.getSalesforceBaseUrl().getHost()+'/services/data/v39.0/query/?q=SELECT+Id,Name,AccountNumber,Type+FROM+Account+limit+10');
        req.setMethod('GET');
        
        //Get SessionId
        string autho = 'Bearer '+userInfo.getSessionId();
        req.setHeader('Authorization', autho);
        
        //Get Response
        Http http = new Http();
        HTTPresponse res= http.send(req);
        string response = res.getBody();
        
        //Deserialize obtained json response
        string str = '['+ response.substring(response.indexOf('records":[')+10,response.indexof(']}')) +']';
        acc = (list<Account>)JSON.deserialize(str,list<Account>.class);
        
        return acc;    
    }set;}
    
}

Visualforce Page:

<apex:page controller="AccountRest">

    <!-- 
    /**
     * Webkul Software.
     *
     * @category  Webkul
     * @author    Webkul
     * @copyright Copyright (c) 2010-2016 Webkul Software Private Limited (https://webkul.com)
     * @license   https://store.webkul.com/license.html
     */
     -->
	<apex:sectionHeader title="Accounts" subtitle="List View"/>
	<apex:pageBlock>
	
		<apex:pageBlockTable value="{!acc}" var="key">
		
			<apex:column>
				<apex:facet name="header">Account Name</apex:facet>
				<apex:outputLink value="/{!key.Id}">{!key.Name}</apex:outputLink>
			</apex:column>
			<apex:column value="{!key.AccountNumber}"/>
			<apex:column value="{!key.Type}"/>	
		
		</apex:pageBlockTable>
	
	</apex:pageBlock>

</apex:page>

Here is the output:

That’s all for how to fetch records of sObjects through REST API in Apex class, still have any issue feel free to add a ticket and let us know your views to make the code better https://webkul.uvdesk.com/en/customer/create-ticket/