Checking is my spawned entity is dead?

Okay so I have spawned an entity using
world.spawnEntity(loc, EntityType.PIG_ZOMBIE);
Now, I want to check if the entity is dead then do something if it is..
I have been told I need to store the entity ID somewhere. But how would java know if its the spawned entity it is referring to? How would I check if the entity is dead? Also where would I store the id of the entity?
Example code please?

 

Code:

Entity e = world.spawnEntity(loc, EntityType.PIG_ZOMBIE);
 
//Later
if(e.isValid()) {

 

adam753
Thanks man!
But would that spawn an entity too?

 

Yes, the code

Code:java

Entity e = world.spawnEntity(loc, EntityType.PIG_ZOMBIE);

both spawns the entity and saves the Entity object returned to the variable, 'e'