Public class BinaryExample{  
    public static void binarySearch(list<integer> integerList, integer key){  
        try{
            integer first=0;
            integer last=integerList.size()-1;
            integer mid = (first + last)/2;
            while( first <= last ){ 
                if ( integerList[mid] < key ){   
                    first = mid + 1;    
                }else if (integerList[mid] == key){  
                    System.debug('Element is found at: ' +  mid);  
                    break;  
                }else{  
                    last = mid - 1;  
                }  
                mid = (first + last)/2;  
            }  
            if ( first > last ){  
                System.debug('Element is not found!');  
            }  
        }catch(exception e){
            system.debug('Error:'+e.getMessage()+'At Line:'+e.getLineNumber());
        }
        
    }
}

list<integer> numval = new list<integer>{10,20,30,40,50,70,80,90,100,110,120,130,150};  
        integer key = 120;  
BinaryExample.binarySearch(numval,key);

output:-

I hope you find the above solution helpful. If it does, please mark as Best Answer to help others too

Thanks and Regards,
Suraj Tripathi