Why is this code not working?

It was working fine before I tried to add an animation. The animation didn't work so I just decided to figure it out later, I deleted everything that involved the animation from the script... then it stopped working! My player (a cube) goes straight through the walls, and when it touches the walls its suppose to stop being able to move in that direction. `using UnityEngine; using System.Collections;

public class Move : MonoBehaviour { public bool canUp = true; public bool canDown = true; public bool canLeft = true; public bool canRight = true;

 void Update()
 {
     if (canUp == true)
     {
         if (Input.GetKeyDown(KeyCode.UpArrow))
         {
             transform.Translate(1f, 0f, 0f);
         }
     }
     if (canDown == true)
     {
         if (Input.GetKeyDown(KeyCode.DownArrow))
         {
             transform.Translate(-1f, 0f, 0f);
         }
     }
     if (canLeft == true)
     {
         if (Input.GetKeyDown(KeyCode.LeftArrow))
         {
             transform.Translate(0f, 0f, 1f);
         }
     }
     if (canRight == true)
     {
         if (Input.GetKeyDown(KeyCode.RightArrow))
         {
             transform.Translate(0f, 0f, -1f);
         }
     }
 }
 void OnCollisionEnter(Collision wall)
 {
     if (wall.gameObject.tag == "TopWall")
     {
         canUp = false;
     }
     if (wall.gameObject.tag == "BottomWall")
     {
         canDown = false;
     }
     if (wall.gameObject.tag == "LeftWall")
     {
         canLeft = false;
     }
     if (wall.gameObject.tag == "RightWall")
     {
         canRight = false;
     }
 }
 void OnCollisionExit(Collision wall)
 {
     if (wall.gameObject.tag == "TopWall")
     {
         canUp = true;
     }
     if (wall.gameObject.tag == "BottomWall")
     {
         canDown = true;
     }
     if (wall.gameObject.tag == "LeftWall")
     {
         canLeft = true;
     }
     if (wall.gameObject.tag == "RightWall")
     {
         canRight = true;
     }
 }

}