Print more than 1 java value

Question

I’m studying matrices. The matrix is in characters information of the game of Thrones. My matrix:

public static String [][] matrizPrincipal() {
        String [] [] matriz = new String [6] [114];
        matriz[0][0] = "Robin Arryn";
        matriz[1][0] = "Lino Facioli";
        matriz[2][0] = "145";
        matriz[3][0] = "Vivo";
        matriz[4][0] = "Arryn";
        matriz[5][0] = "Masculino";

        matriz[0][1] = "Yohn Royce";
        matriz[1][1] = "Rupert Vansittart";
        matriz[2][1] = "45";
        matriz[3][1] = "Vivo";
        matriz[4][1] = "Arryn";
        matriz[5][1] = "Masculino";
        return matriz;
    }

Yes, it’s not complete.

Linha 0: Nome Personagem
Linha 1: Ator
linha 2: Temporadas que participa
Linha 3: Vivo ou morto
Linha 4: Família
Linha 5: Genero

I’m having trouble with the method that returns the character of a certain season. The user types the desired season, and the method will print all the active characters in it. I have the method ready now, I’m only in trouble at the time of return.

Method:

public static String imprimeMatrizQualTemporada(String temporada, String [] [] mat) {
    for(int i = 0; i < mat.length; i++) {
        for(int j = 0; j < mat[i].length; j++) {
            if(mat[2][j].contains(temporada)) {
                System.out.println(mat[0][j] + "\n");
            }
        }
    }
    return "Não encontramos um personagem com este nome";
}

The String season and String mat comes from the main method, where season is the season the guy wants to know which characters are.

When compiling the above method, no problem, but when executing I have the following error:

The most bizarre, is that despite the error it returns the right result:

Just don’t know why this mistake, which points to the following if:

if(mat[2][j].contains(temporada)) {
    System.out.println(mat[0][j] + "\n");
}

One thing I’m sure of. It has to do with this System.out.println, 'Cause when I try to do it this way:

if(mat[2][j].contains(temporada)) {
    return mat[0][j];
}

Using return, it works perfectly, but only returns the first character, and not all.

Updating: Full code below to improve visualization

import java.util.Scanner;

public class matriz {

    public static void main(String args[]) {
        System.out.println("\f");
        String [][] mat = matrizPrincipal();
        System.out.println("1.Listar atores e suas respectivas temporadas.");
        Scanner in = new Scanner(System.in);
        String msg = in.nextLine();
        int opcao = Integer.parseInt(msg);        
        switch(opcao) {
            case 1:
                System.out.println("Digite a temporada à se verificar");
                String temporada = in.nextLine();
                String resultado2 = imprimeMatrizQualTemporada(temporada,mat);
                System.out.println("Personagens nesta Temporada:" +resultado2);
                break;
        }
    }

    public static String [][] matrizPrincipal() {
        String [] [] matriz = new String [6] [114];
        matriz[0][0] = "Robin Arryn";
        matriz[1][0] = "Lino Facioli";
        matriz[2][0] = "145";
        matriz[3][0] = "Vivo";
        matriz[4][0] = "Arryn";
        matriz[5][0] = "Masculino";

        matriz[0][1] = "Yohn Royce";
        matriz[1][1] = "Rupert Vansittart";
        matriz[2][1] = "45";
        matriz[3][1] = "Vivo";
        matriz[4][1] = "Arryn";
        matriz[5][1] = "Masculino";
        return matriz;
    }

    public static String imprimeMatrizQualTemporada(String temporada, String [] [] mat) {
        for(int i = 0; i < mat.length; i++) {
            for(int j = 0; j < mat[i].length; j++){
                if(mat[2][j].contains(temporada)){
                    System.out.println(mat[0][j] + "\n");
                }
            }
        }
        return "Não encontramos um personagem com este nome";
    }

}

Answer 1

The error is due to the fact that you declare the matrix to have 6 rows and 114 columns and only assign values to 6 rows and 2 columns.

The value returned by mat.length; is 6 and mat[i].length; is 114.
In the course of both loops iand j will point to matrix elements that have not been initialized, hence the NullPointerException.

You should change the line:

String [] [] matriz = new String [6] [114];

To:

String [] [] matriz = new String [6] [2];

Mistakes aside, also its matrix is poorly formed, its dimensions should be reversed:[2] [6].
Each character should be assigned to a row and its characteristics assigned to the columns.
On the other hand only one is needed loop to get the result you want.
Given this your code would be like this:

import java.util.Scanner;

public class matriz {

    public static void main(String args[]) {
        System.out.println("\f");
        String [][] mat = matrizPrincipal();
        System.out.println("1.Listar atores e suas respectivas temporadas.");
        Scanner in = new Scanner(System.in);
        String msg = in.nextLine();
        int opcao = Integer.parseInt(msg);        
        switch(opcao) {
            case 1:
                System.out.println("Digite a temporada à se verificar");
                String temporada = in.nextLine();
                String resultado2 = imprimeMatrizQualTemporada(temporada,mat);
                System.out.println("Personagens nesta Temporada:" +resultado2);
                break;
        }
    }

    public static String [][] matrizPrincipal() {
        String [] [] matriz = new String [2] [6];
        matriz[0][0] = "Robin Arryn";
        matriz[0][1] = "Lino Facioli";
        matriz[0][2] = "145";
        matriz[0][3] = "Vivo";
        matriz[0][4] = "Arryn";
        matriz[0][5] = "Masculino";

        matriz[1][0] = "Yohn Royce";
        matriz[1][1] = "Rupert Vansittart";
        matriz[1][2] = "45";
        matriz[1][3] = "Vivo";
        matriz[1][4] = "Arryn";
        matriz[1][5] = "Masculino";
        return matriz;
    }
    public static String imprimeMatrizQualTemporada(String temporada, String [] [] mat) {
        for(int i = 0; i < mat.length; i++) {
            if(mat[i][2].contains(temporada)){
                System.out.println(mat[i][0] + "\n");
            }
        }
        return "Não encontramos um personagem com este nome";
    }
}

See on Ideone