JAVA 2D Array Loop Print Formatting [0][0], [1][1], etc

Question

I am having trouble getting my 2D array to print side by side values taking the first array row value index 0 and matching it to the 2nd row array index 0 and continuing on in a vertical list. As it stands, my code compiles and just prints the entire arrays in a horizontal fashion on two lines. Basically, I would like the end result to be formatted like this:

Admin | Password1
Vale.Vicky | BruceIsTheBat!
Lane.Lois | FlyMeToTheMoon1234
Kent.Clark | PhoneBoothsSmell
Wayne.Bruce | ThisBat4You99

...and so on.

public class PasswordArrays {                   // start of class

public static void main(String[] args) {        // Start of main
    // TODO Auto-generated method stub

    String [][] idArray = {
            {"Admin", "Vale.Vicky", "Lane.Lois", "Kent.Clark", "Wayne.Bruce", "Parker.Peter", "Rogers.Steve", "Luther.Lex", "Osborn.Harry","Prince.Diana", "Linda Zoel"},
            {"Password1", "BruceIsTheBat!", "FlyMeToTheMoon1234", "PhoneBoothsSmell","ThisBat4You99", "webSlinger","ShieldEnthusiast", "HairClub4Men", "GoblinGoober", "WonderWonderWho?", "WhoIsLindaZoel?"}
            };

    printArray(idArray);

} //End of main
public static void printArray(String a [][]) {      //start of printArray method

    for (int row=0; row < a.length ; row++) {       // start of row for loop    

        for (int column = 0; column < a [row].length; column++) {       //start of column for loop

            System.out.print(a[row][column] + " ");

        } // End of column for loop

        System.out.println();

    } // End of row for loop


} // End of printArray method

} //End of class

I know there's got to be an answer already for this somewhere but I have been unsuccessful in finding it. Any help is greatly appreciated.

It looks like you need to learn to use a debugger. Please help yourself to some complementary debugging techniques. If you still have issues afterwards, please feel free to come back with a more specific question. — Joe C
– Joe C, Commented Feb 21, 2018 at 21:17
IntStream.range(0, idArray[0].length).map(i -> idArray[0][i] + " | " + idArray[1][i]).forEach(System.out::println); — shmosel
– shmosel, Commented Feb 21, 2018 at 21:32

babybear · Accepted Answer · 2018-02-21 22:15:04Z

3

A 2D array could be iterated in two ways:

Row wise
Column wise

As per your expected result, what you would want to do is iterate column wise rather than row wise. Here's a solution:

public static void printArray(String a [][]) {

    for(int col=0; col < a[0].length; col++) {
        for (int row = 0; row < a.length; row++) {
            if (row!=a.length-1) {
                System.out.print(a[row][col] + "|");
            }
            else {
                System.out.print(a[row][col]);
            }
        }
        System.out.println();
    }
}

Helpful Link: Iterate through multi-dimensional array

answered Feb 21, 2018 at 22:15

babybear

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Comments

AppleCiderGuy · Accepted Answer · 2018-02-21 21:51:57Z

3

you are traversing your 2D array incorrectly

you can try this for your array:

if(a.length > 0){
  for(int i = 0; i < a[0].length; i++){
    for(int j = 0;j < a.length; j++){
      System.out.print(a[j][i]+" ");
    }
    System.out.println("");
  }
}

answered Feb 21, 2018 at 21:51

AppleCiderGuy

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1 Comment

AppleCiderGuy Over a year ago

replace your nested for loop with this and it will work

Zabuzard · Accepted Answer · 2018-02-21 21:33:42Z

Structure

Are you sure that you understood the structure of your 2d-array? You only have two rows but multiple columns (the array contains 2 arrays containing multiple elements each).

The structure is

idArray = { /* firstArray, secondArray */ }

idArray[0] = { /* Names */ }
idArray[1] = { /* Passwords */ }

Solution

You only need one iteration from int i = 0; to i < idArray[0].length. After that always pair the content of idArray[0][i] with idArray[1][i], that's all.

final int[][] idArray = ...

// Variant 1: Regular for-loop
for (int i = 0; i < idArray[0].length; i++) {
    System.out.println(idArray[0][i] + " | " + idArray[1][i];
}

// Variant 2: Stream solution
IntStream.range(0, idArray[0].length)                 // IntStream
    .map(i -> idArray[0][i] + " | " + idArray[1][i])  // Stream<String>
    .forEach(System.out::println);

Note that idArray[0].length and idArray[1].length should of course be equal.

Notes

Probably you are better off using proper OOP, creating classes for each Account containing name and password fields and then using a List<Account> and toString for Account or something like that.

public class Account {
    private final String mName;
    private final String mPassword;

    public Account(final String name, final String password) {
        this.mName = name;
        this.mPassword = password;
    }

    public String getName() {
        return this.mName;
    }

    public String getPassword() {
        return this.mPassword;
    }

    @Override
    public String toString() {
        return this.getName() + " | " + this.getPassword();
    }
}

And then use it like

final List<Account> accounts = new ArrayList<>();
accounts.add(new Account("Admin", "Password1"));
...

// Variant 1: Enhanced for-loop 'foreach'
for (final Account account : accounts) {
    System.out.println(account);
}

// Variant 2: The same using streams
accounts.forEach(System.out::println);

// Variant 3: Using Lists 'toString'
System.out.println(accounts);

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