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Android Build an Interactive Story App (Retired) The Model-View-Controller Pattern Adding a Custom Constructor

Posted by ariel varon
ariel varon
678 Points

What is the error here?

Hi, I got this error java.lang.NullPointerException (Look around JavaTester.java line 100) while working on this challenge and I can't quite figure out what was wrong with it. The challenge was to set a custom constructor that uses a String parameter which is exactly what i did... can anyone please help?

Thank you.

P.S. If this is about the "use this parameter to make mType a specific kind of spaceship" then that's just vague wording of the challenge.

Spaceship.java 
public class Spaceship {
    public String mType;

  public Spaceship(){
  mType = "SHUTTLE";
  }

  public Spaceship(String type1){

    type1 = mType;

  }

    public String getType() {
      return mType;
    }

    public void setType(String type) {
      mType = type;
    }
}
Victor Svetuskin
Victor Svetuskin
5,015 Points

I think you should assign type1 to mType, not viseversa.

public Spaceship(String type1) {
mType = type1;
}

1 Answer

Evan Demaris
Evan Demaris
64,262 Points
Evan Demaris
Evan Demaris
64,262 Points

Hi Ariel,

You've assigned the argument to be mType instead of assigning mType to be the argument. Because mType has been initialized but not declared to be anything yet, it's "null"; assigning type1 to "point" to an undeclared variable is where that error message is coming from.

Hope that helps!