Fixed camera on rails.

You have to code this sort of thing manually and there are endless techniques that can be used to achieve varying results. Here's how to get the camera to follow an object on the X and Y axes to get you started.

 //set this to the object to follow
 public GameObject followObject;
 
 //I recommend moving the camera in the LateUpdate method
 void LateUpdate()
 {
     Vector3 camPos = Camera.main.transform.position;
     camPos.x = followObject.transform.position.x;
     camPos.y = followObject.transform.position.y;
     Camera.main.transform.position = camPos;
 }

EDIT: Attempted java version (I don't use java, there may be mistakes):

 //set this to the object to follow
 var followObject : GameObject;
 
 //I recommend moving the camera in the LateUpdate method
 function LateUpdate()
 {
     var camPos : Vector3 = Camera.main.transform.position;
     camPos.x = followObject.transform.position.x;
     camPos.y = followObject.transform.position.y;
     Camera.main.transform.position = camPos;
 }