String [][] Output issues

Question

I am trying to write a program that i need to output a 2 dimensional array for a list of first and last names entered by the user. When I try running the program there is no errors, but it gives me this for output:

[[Ljava.lang.String;@b8f82d, [Ljava.lang.String;@1ad77a7,     
[Ljava.lang.String;@18aaa1e, [Ljava.lang.String;@a6aeed,   
[Ljava.lang.String;@126804e, [Ljava.lang.String;@b1b4c3, 
[Ljava.lang.String;@d2906a, [Ljava.lang.String;@72ffb, 
[Ljava.lang.String;@1df38fd, [Ljava.lang.String;@16a786, 
[Ljava.lang.String;@1507fb2, [Ljava.lang.String;@1efb836, 
[Ljava.lang.String;@126e85f, [Ljava.lang.String;@161f10f, 
[Ljava.lang.String;@1193779, [Ljava.lang.String;@8916a2, 
[Ljava.lang.String;@2ce908, [Ljava.lang.String;@77158a, 
[Ljava.lang.String;@27391d, [Ljava.lang.String;@116ab4e, 
[Ljava.lang.String;@148aa23, [Ljava.lang.String;@199f91c, 
[Ljava.lang.String;@1b1aa65, [Ljava.lang.String;@129f3b5, 
[Ljava.lang.String;@13f3045, [Ljava.lang.String;@17a29a1,  
[Ljava.lang.String;@1434234, [Ljava.lang.String;@af8358, 
[Ljava.lang.String;@d80be3, [Ljava.lang.String;@1f4689e,  
[Ljava.lang.String;@1006d75, [Ljava.lang.String;@1125127, 
[Ljava.lang.String;@18dfef8, [Ljava.lang.String;@15e83f9,  
[Ljava.lang.String;@2a5330] 

BUILD SUCCESSFUL (total time: 0 seconds)

This is my code:

package assignment_6_1;
import java.util.Scanner;
import java.util.Arrays;
public class Assignment_6_1 {

    public static void main(String[] args) {
        //Create a Scanner
        Scanner input = new Scanner(System.in);
        //Create int & string []
        String[][]firstAndLastNames = new String[36][2];
            int[]heightOfPerson = new int[36];

        //Gather list of names and heights
        for(int i=0; i<heightOfPerson.length; i++)
        {
            //Get first name
            System.out.println("Enter Your First Name " + "Passenger #" + i+1 + ": ");
            firstAndLastNames[1][i] = input.next();

            //Get last name
            System.out.println("Enter Your Last Name " + "Passenger #" + i+1 + ": ");
            firstAndLastNames[2][i] = input.next();

            //Get height in inches
            System.out.println("Enter your height (Iches) " + "Passenger #" + i+1 + ": ");
            heightOfPerson[i] = input.nextInt();

            if(firstAndLastNames[36][2] != null){
            System.out.println(Arrays.deepToString(firstAndLastNames));
            break;}
        }
    }
}

I then have to output the height of the person but I have not gotten that far yet.

Answer 1

Don't use Arrays.toString(array). Use Arrays.deepToString(array). It will print multi-dimensional arrays.

    String[][] array = new String[][] {
            { "Apple", "Pear", "Fruit" },
            { "Pi", "Rho", "Omega" }, 
            { "Jack", "Jill", "Joe" } 
    };

    System.out.println(Arrays.deepToString(array));

    //Prints: [[Apple, Pear, Fruit], [Pi, Rho, Omega], [Jack, Jill, Joe]]

Answer 2

You are stringifying the outer array, but the inner arrays are not handled. What you need to do is to build the output by iterating over the outer array.

This should help:

for (String[] firstAndLastName : firstAndLastNames) {
    System.out.println(firstAndLastName[0] + ", " + firstAndLastName[1]);
}

Alternatively you can store the user details in a User object. Then, if you define a toString method on that object thhe original Arrays.toString call will produce more legible output.

class User {
    private String firstName, lastName;

    public User(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;
    }

    ...

    public String toString() {
        return firstName + ", " + lastName;
    }
}

Also, as nielsen points out your for loop has the wrong loop test on it. You have an empty array at the moment so you need to address that as well.

Answer 3

Maybe you should not do

 for(int i=0; i>35; i++)

but rather

for(int i=0; i<35; i++)

Answer 4

You are trying to store the last name in a place that does not exist in your array!

You are declaring your array like this:

String[][]firstAndLastNames = new String[35][1];

This means you have 35 rows, and 1 column. Arrays start at index zero. Not one.

When you are trying to store your last names:

firstAndLastNames[i][1] = input.next();

You are not calling the correct column index. Change the array delcaration line line to this:

String[][]firstAndLastNames = new String[35][2]; //now we have 2 columns

Once you store the data correctly, you need to iterate through the array to properly display your data.

try the following code:

public static void main(String[] args) {
        String[][] array = new String [3][2]; //Notice how the column declaration is now '2'. This means available indexes are 0 and 1.
        Scanner scn = new Scanner (System.in);
        for (int i = 0; i < array.length; i++) {
            System.out.println ("Enter data " + i + ")");
            array[i][0] = scn.nextLine();
        }
        array[0][1] = "1"; //Understand why this works now?
        array[1][1] = "2";
        array[2][1] = "3";  

        for (int i = 0; i < array.length; i++) {
             for (int k = 0; k < 2; k++) {
                 System.out.println((array[i][k]));
             }
        }

    }

Answer 5

Answer by matthew is perfect but if we do small change in concat operation then it will become more fluent for eg.

 public static void main(String...args) {

    String[][] firstAndLastName =  {
            {"Bob","Martin"},
            {"Martin","Fowler"}
    };

    for(String[] name : firstAndLastName) {
        System.out.println(toString(name));
    }
}

---

 private static String toString(String[] a) {
    int iMax = a.length - 1;

    StringBuilder b = new StringBuilder();

    for (int i = 0; ; i++) {
        b.append(a[i]);
        if (i == iMax)
            return b.toString();
        b.append(", ");
    }
}