Add ArrayList into another ArrayList

Question

I have two classes:

Products:

01; Desinfectante
02; Aerosol
03; Limpia Vidrio
04; Desengrasante
05; Mata mosquitos
06; Mata cucarachas
07; Aceite en aerosol

Instructions:

01;1;Elevar la masa hasta llegar a tal punto;0;10
01;1;Mezclar este material con anterior;1;15
01;2;Relevar;2;5
01;3;Llevar;00;0
02;1;Descripcion;7;2
02;2;Descripcion;6;2
02;2;Descripcion;00;0
03;1;Descripcion;1;1
03;1;Descripcion;2;9
03;2;Descripcion;00;0
03;3;Descripcion;5;2
03;4;Descripcion;6;2
03;4;Descripcion;3;10
04;1;Descripcion;00;0
04;2;Descripcion;1;2
04;3;Descripcion;1;0
04;3;Descripcion;2;2
04;3;Descripcion;3;2
04;4;Descripcion;7;1
04;4;Descripcion;6;2
05;1;Descripcion;7;20
05;1;Descripcion;6;9
05;2;Descripcion;00;0
05;3;Descripcion;1;2
05;3;Descripcion;2;10
06;1;Descripcion;2;12
06;1;Descripcion;4;1
06;1;Descripcion;6;8
06;2;Descripcion;5;4
06;2;Descripcion;7;2
07;1;Descripcion;1;12
07;1;Descripcion;2;2
07;2;Descripcion;3;19
07;2;Descripcion;4;4
07;2;Descripcion;00;2
07;2;Descripcion;5;12

The thing is this: i have to insert the instructions ArrayList into the Products. The link between them is the first number, that is the code of the product.

I tried two things, the first one:

public static ArrayList<Productos> InsertInstInProd(ArrayList<Instrucciones> instructions, ArrayList<Productos> products)
{ 
    for (int i = 0; i < products.size()-1; i++)
    {
        int n = 0;
        for (int j = 0; j < instructions.size()-1; j++)
        {
            int first = products.get(i).getNumero();
            int second = instructions.get(j).getCodProd();

            if (first == second)
            {
                products.get(i).getInstr().get(n).setCodIns(instructions.get(j).getCodIns());
                products.get(i).getInstr().get(n).setCodProd(instructions.get(j).getCodProd());
                products.get(i).getInstr().get(n).setDescr(instructions.get(j).getDescr());
                products.get(i).getInstr().get(n).setMat(instructions.get(j).getMat());
                products.get(i).getInstr().get(n).setMatNec(instructions.get(j).getMatNec());

                n++;
            }
        }
        n = 0;
    }

The second one:

public static ArrayList<Productos> InsertInstInProd(ArrayList<Instrucciones> instructions, ArrayList<Productos> products)
{ 
    for (int i = 0; i < products.size()-1; i++)
    {
        int n = 0;
        for (int j = 0; j < instructions.size()-1; j++)
        {
            int first = products.get(i).getNumero();
            int second = instructions.get(j).getCodProd();

            if (first == second)
            {
                products.get(i).setInstr(instructions);
                n++;
            }
        }
        n = 0;
    }

    return products;
}

In the first case i've got this: Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0 In the second one it doesn't work, it doesn't validate the codes of the product, so it's useless. I don't know what I'm doing wrong. — madf1990
– madf1990, Commented Jul 11, 2015 at 3:14

Karthik · Accepted Answer · 2015-07-11 04:03:27Z

1

You are getting NullPointerException because of

     products.get(i).getInstr().get(n).setCodIns(instructions.get(j).getCodIns());

You are not checking whether the list products.get(i).getInstr() has elements or not. When the list is empty and when you are accessing it as products.get(i).getInstr().get(0) it's throwing you NullPointerException because trying to get the first element of an empty list. So before you do this operation, make sure that products.get(i).getInstr() is not empty.

If they are of same type, you can directly add the whole arraylist :

   products.get(i).getInstr().addAll(instructions); // again make sure that is not empty.

If you just want to replac, use :

    products.get(i).setInstr(instructions.get(j));

edited Jul 11, 2015 at 4:03

answered Jul 11, 2015 at 3:22

Karthik

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2 Comments

madf1990 Over a year ago

ok, and how can I add the entire ArrayList (instructions) to products.get(i).getInstr() ?

madf1990 Over a year ago

yeah, i've tried that, but the thing is that all the ArrayList goes there, and I want only that line. products.get(i).setInstr(instructions).get(j);

vijayinani · Accepted Answer · 2015-07-11 03:47:38Z

Products Class



    package productsandinstructions;

    import java.util.List;

    public class Product {
        private int productId;
        private String productName;
        private List instructions;

        public int getProductId() {
            return productId;
        }

        public void setProductId(int productId) {
            this.productId = productId;
        }

        public String getProductName() {
            return productName;
        }

        public void setProductName(String productName) {
            this.productName = productName;
        }

        public List getInstructions() {
            return instructions;
        }

        public void setInstructions(List instructions) {
            this.instructions = instructions;
        }
    }

Instruction Class



    package productsandinstructions;

    public class Instruction {
        private int productId;
        private int instructionId;
        private String instDesc;
        private int mat;
        private int matNec;
        private boolean done;

        public int getProductId() {
            return productId;
        }

        public void setProductId(int productId) {
            this.productId = productId;
        }

        public int getInstructionId() {
            return instructionId;
        }

        public void setInstructionId(int instructionId) {
            this.instructionId = instructionId;
        }

        public String getInstDesc() {
            return instDesc;
        }

        public void setInstDesc(String instDesc) {
            this.instDesc = instDesc;
        }

        public int getMat() {
            return mat;
        }

        public void setMat(int mat) {
            this.mat = mat;
        }

        public int getMatNec() {
            return matNec;
        }

        public void setMatNec(int matNec) {
            this.matNec = matNec;
        }

        public boolean isDone() {
            return done;
        }

        public void setDone(boolean done) {
            this.done = done;
        }
    }

Main Class



    package productsandinstructions;

    import java.util.List;

    public class ProductsAndInstructionsMain {

        private List products;
        private List instructions;

        public List getProducts() {
            return products;
        }

        public void setProducts(List products) {
            this.products = products;
        }

        public List getInstructions() {
            return instructions;
        }

        public void setInstructions(List instructions) {
            this.instructions = instructions;
        }

        public static void main(String[] args) {
            ProductsAndInstructionsMain main = new ProductsAndInstructionsMain();
            main.mergeProductsAndInstructions();
        }

        public void mergeProductsAndInstructions() {
            for (Product product : products) {
                for (Instruction instruction : instructions) {
                    if ((!(instruction.isDone())) && (instruction.getProductId() == product.getProductId())) {
                        product.getInstructions().add(instruction);
                        instruction.setDone(true);
                    }
                }
            }
        }
    }

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