Null Pointer exception

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.

Quote:

---

Originally Posted by diegoyj

Code:

---

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.

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);

Quote:

---

Originally Posted by diegoyj

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

---

Did you also fix your indentation?

kind regards,

Jos

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();
}
}
}

Quote:

---

Originally Posted by diegoyj

I add two new brackets.

Code:

---

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

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

Quote:

---

Originally Posted by diegoyj

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