How can I get my dog to stop barking at other dogs on the street?

I agree with Nicole. Your boy is likely expressing excitement at seeing the new dog and frustration that he can't greet them fast enough. In addition to using treats, you can bring along a favorite toy (I find a squeaky ball is a good option for distracting a barking dog since most dogs find them captivating) or even just changing your pace/direction suddenly, like veering off at a jog while talking to your dog happily. I use the latter quite a bit with my dog who gets hyper-focused on dogs she spots; if she starts staring, I'll pick up my speed and tell her "come on! let's go!" and such in a happy, higher pitched voice to make myself more interesting. If I catch her early enough/at a great enough distance, this redirects her from trying to stare the dog down to playing with me. Ideally you want him to spot the other dog, but engage in another behavior before he starts barking. It will probably take some fine-tuning of the method and the distance away you have to be to get the desired results, but if you make it into a game (spotting dogs and then doing something fun, like eating treats, playing with a toy, or jogging) it can help you both enjoy your walks a lot more.

My dog does this too, only out of fear. I've found it helpful to try and distract him. Bring along treats and see if you can get his attention (sit and make eye contact with you) and if he does, reward him. It also helps if you're able to step in front of him to block his gaze. It can get tedious, but oftentimes I have to stop on the side of the street, stand in front of my dog, make him sit, and keep his gaze blocked until the other dog passes by.