Null Pointer exception

[diegoyj]

for (BaseCell c : cells) {
if (c != null && c.isAlive())
c.eat();
if (c.type == "AnimalCell"){
BaseCell a;
a = new PlantCell();
int k=c.getLocation();
a = BuscarLista(k);
a.setFoodLevel(a.getFoodLevel() - 1);
a.doStarvation();
}

}

Hi, Sometimes when I run this code, gives me this error:

Exception in thread "main" java.lang.NullPointerException
at Sim.run(Sim.java:117)
at Sim.main(Sim.java:175)

It usually happens 1 in 5 times I run. I don´t know which is the problem.

[JosAH]

for (BaseCell c : cells) {
			 if (c != null && c.isAlive())
				 c.eat();
			 	if (c.type == "AnimalCell"){
			 		BaseCell a;
					a = new PlantCell();
			 		int k=c.getLocation();
			 		a = BuscarLista(k);
			 		a.setFoodLevel(a.getFoodLevel() - 1);
			 		a.doStarvation();
			 		}
			 		
			 	}

Hi, Sometimes when I run this code, gives me this error:

Exception in thread "main" java.lang.NullPointerException
at Sim.run(Sim.java:117)
at Sim.main(Sim.java:175)

It usually happens 1 in 5 times I run. I don´t know which is the problem.

You indented the second "if ( ... )" statement as if it were part of the "if (c != null ...)" statement; it isn't because you forgot a few curly braces. You also can't compare Strings for equality with the == operator, use the .equals() method for that. Read the API documentation for the String class.

kind regards,

Jos

ps. next time use [ code ] ... [ /code ] tags; I only saw your indentation when I wanted to reply.

[diegoyj]

Ok, To campare strings i use the .equals() method , and have the same error.
The error is in the instruction 9.
a.setFoodLevel(a.getFoodLevel() - 1);

[JosAH]

Ok, To campare strings i use the .equals() method , and have the same error.

Did you also fix your indentation?

kind regards,

Jos

[diegoyj]

I add two new brackets.
for (BaseCell c : cells) {
if (c != null && c.isAlive()){
c.eat();
if (c.type.equals("AnimalCell")){
BaseCell a;
a = new PlantCell();
int k=c.getLocation();
a = BuscarLista(k);
a.setFoodLevel(a.getFoodLevel() - 1);
a.doStarvation();
}
}
}

[JosAH]

I add two new brackets.

 for (BaseCell c : cells) {
			 if (c != null && c.isAlive()){
				 c.eat();
			 	if (c.type.equals("AnimalCell")){
			 		BaseCell a;
					a = new PlantCell();
			 		int k=c.getLocation();
			 		a = BuscarLista(k);
			 		a.setFoodLevel(a.getFoodLevel() - 1);
			 		a.doStarvation();
			 		}
			 }
		}

Please use those [ code ] ... [ /code ] tags and be a bit more informative please; don't make us guess; what is the line where that NullPointerException was thrown?

kind regards,

Jos

[diegoyj]

The error is in the instruction 9.
a.setFoodLevel(a.getFoodLevel() - 1);

[JosAH]

The error is in the instruction 9.
a.setFoodLevel(a.getFoodLevel() - 1);

Most likely your error is in the previous line: "a = BuscarLista(k);" Check if that method (that should start with a lowercase letter) returns null. System.out.println( ... ) is your friend here.

kind regards,

Jos