Enemy Ai Set up java

I am new to unity3d . I want the animation to play when player enters . I don't know what I am doing wrong. Please help me . I only gotten one animation to work. But the animation only works if I set on set layer as default. I trying to get two animations working . Here is my code :

var anim: Animation;

function Start() { anim == GetComponent.<Animation>(); anim.Play("attack");

//wait for the animation to finish. yield WaitForSeconds(anim.clip.lenth); }

function Update() {

}