fixing nullpointerexception error in java

Question

here is my code. i keep getting a nullpointerexception in my sort and print method, it starts on the line with the for loop with allAnimals.length. I think the array allAnimal in the class, isnt filled in getData as it should. allAnimal in getData method isnt being treated as allAnimal in the class. Basically all other methods still think allAnimal is null. I am no master in java so if someone could please tell me how to fix this error, or give me tips on how to avoid it I would greatly appreciate it.

public class Animal {
//data fields 
private String name;
private int birthYear;
private String species;
private float balance;
private String ownersName;
static Animal[] allAnimal;


public Animal(){
    //no-arg constructor 
}

public Animal(String name, int birthYear, String species, float balance, String ownersName){
    // constructor builds animal template
    this.name = name;
    this.birthYear = birthYear;
    this.species = species;
    this.balance = balance;
    this.ownersName = ownersName;
}


//set and get for name
public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

//set and get for birth year
public int getBirthYear() {
    return birthYear;
}

public void setBirthYear(int birthYear) {
    this.birthYear = birthYear;
}

//set and get for species
public String getSpecies() {
    return species;
}

public void setSpecies(String species) {
    this.species = species;
}

//set and get for balance
public float getBalance() {
    return balance;
}


public void setBalance(float balance) {
    this.balance = balance;
}

//set and get for owner
public String getOwnersName() {
    return ownersName;
}

public void setOwnersName(String ownersName) {
    this.ownersName = ownersName;
}







public static void getData(){

    System.out.println("How many animals are in this report? ");
    Scanner kb = new Scanner(System.in);

    int length = kb.nextInt();
    Animal[] allAnimal = new Animal[length]; 

    System.out.println("input: animal name, birth year, species, bill balance and owner's name.");
    //fill array of objects with data
    int i;
    for(i = 0; i < allAnimal.length; i++){

        allAnimal[i] = new Animal(kb.next(), kb.nextInt(), kb.next(), kb.nextFloat(), kb.next());
    }


}//end getData


public static void sortData(Animal[] allAnimal){
    Animal temp;
    int i,j;
    for(i = 0; i < allAnimal.length; i++){  
        for(j = i + 1; j < allAnimal.length; j++){


            if(allAnimal[i].getBalance() > allAnimal[j].getBalance() ){ //swap big with small
                temp = allAnimal[j];
                allAnimal[j] = allAnimal[i];
                allAnimal[i] = temp;
            }
        }
    }
}//end sortData


    public static void printData(Animal[] allAnimal){
        int i;
        for(i = 0; i < allAnimal.length; i++){
        System.out.println("Pet Name: " + allAnimal[i].getName() + " Birth year: " +
                allAnimal[i].getBirthYear() + " Species: " + allAnimal[i].getSpecies() +
                " Balance due: " + allAnimal[i].getBalance() + " Owner: " + allAnimal[i].getOwnersName());
        }
    }


   public static void main(String[] args){
       getData();
       sortData(allAnimal);
       printData(allAnimal);

   }//end main 

}//end class

NPE · Accepted Answer · 2013-10-26 07:01:40Z

2

You have two variables named allAnimal:

static Animal[] allAnimal;
Animal[] allAnimal = new Animal[length];

You initialize one and then use the other (which is still null).

In getData(), change

Animal[] allAnimal = new Animal[length];

to

allAnimal = new Animal[length];

There could be other problems, I didn't look too closely.

answered Oct 26, 2013 at 7:01

NPE

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Comments

Prabhakaran Ramaswamy · Accepted Answer · 2013-10-26 07:04:15Z

0

You are creating local variable Animal[] allAnimal within getData() method that caused the problem.

Problem here

public static void getData(){

    Animal[] allAnimal = new Animal[length];  //here is the problem
}

fix it like below.

public static void getData(){

    allAnimal = new Animal[length];  //here is the fix
}

answered Oct 26, 2013 at 7:04

Prabhakaran Ramaswamy

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Comments

Crickcoder · Accepted Answer · 2013-10-26 07:04:49Z

0

You have only declared AllAnimal at the class level :

static Animal[] allAnimal;

Now, in your method getData() you have declared and initialized a local variable allAnimal. Note that it has nothing to do with the one at class level.

Animal[] allAnimal = new Animal[length];

In other methods you are trying to use class level allAnimal which will throw a null pointer inless it is initiatlized.

for(i = 0; i < allAnimal.length; i++){

answered Oct 26, 2013 at 7:04

Crickcoder

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