Declaring an array of strings that can be directly printed Java

Question

Given this class:

public class Book {
    private String bookName;
    private String[] chapters = new String[9];
    private int numberOfChapters;

    public Book(String bn){
        bookName = bn;
    }
    public Book(String b[]){
        chapters = b;
    }
    public void addChapter(String chapter){
        chapters[numberOfChapters] = chapter;
        numberOfChapters++;
    }
    public String[] getChapter(){
        return chapters;
    }
    public int getNumberOfChapters(){
        return numberOfChapters;
    }
    public String getBookName(){
        return bookName;
    }
    public String toString(){
        return("Book Name: " + getBookName() + " chapters[] = " + getChapter() + " number of chapters :  " + getNumberOfChapters());
    }

}

I need to write a driver that creates an array of chapters (strings), then assigns each object within it to the Book object. My problem is that when I do this, the toString() method doesn't print the chapters properly, and instead returns the memory address.

Here's what I have so far:

public class BookTest {

    public static void main(String[] args) {
        String[] BookArray = new String[9];
        for(int i = 0; i<BookArray.length; i++){
            BookArray[i] = new String("Chap"+(i+1));
        }
        Book b1 = new Book("Name1");
        for(int i=0; i<BookArray.length; i++){
            b1.addChapter(BookArray[i]);
        }
        System.out.println(b1.toString());
    }
}

Which prints

Book Name: Name1 chapters[] = [Ljava.lang.String;@2a139a55 number of chapters :  9

What do I need to change in my driver to properly print the chapters, without changing the toString() method?

Please don't make more work for others by vandalizing your posts. By posting on the Stack Exchange (SE) network, you've granted a non-revocable right, under a CC BY-SA license, for SE to distribute the content (i.e. regardless of your future choices). By SE policy, the non-vandalized version is distributed. Thus, any vandalism will be reverted. Please see: How does deleting work? …. If permitted to delete, there's a "delete" button below the post, on the left, but it's only in browsers, not the mobile app. — Makyen
– Makyen ♦, Commented Nov 16, 2019 at 16:26

Jesper · Accepted Answer · 2015-12-05 16:58:25Z

2

Use Arrays.toString(getChapter()) in your toString method. I would rather use a List<String> instead of a String array, it's easier to add and remove chapters from the book. Or maybe a Map<int, String>, that way you can add chapters with both an ID (e.g. chapter 12) and a name for each chapter.

answered Dec 5, 2015 at 16:58

Jesper

2,2344 gold badges26 silver badges33 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

agsl Over a year ago

Is there any way to get it working without modifying the class?

Jesper Over a year ago

@agsl well no, not without changing the toString method of Book. When you print an Array, you print the memory address, not the contents of the Array.

Robin Spiess · Accepted Answer · 2015-12-05 16:55:16Z

0

Use the function

Arrays.toString(chapters)

to get a nice output.

answered Dec 5, 2015 at 16:55

Robin Spiess

1,4809 silver badges17 bronze badges

1 Comment

Lal Over a year ago

Provide some kind of explanation too to support your answer.

Community · Accepted Answer · 2017-05-23 11:44:40Z

0

Array is Object in Java.

the Java Language Specification writes:

In the Java programming language arrays are objects (§4.3.1), are dynamically created, and may be assigned to variables of type Object (§4.3.2). All methods of class Object may be invoked on an array.

Hence Ljava.lang.String;@2a139a55 is printed.

Refer to Is it possible in Java to override 'toString' for an Objects array?

edited May 23, 2017 at 11:44

CommunityBot

11 silver badge

answered Dec 5, 2015 at 17:02

Ashish Nijai

3293 silver badges14 bronze badges

Comments

Desaretiuss · Accepted Answer · 2015-12-05 17:03:34Z

0

The function getChapters() returns the memory address, doesn't print the array.

To do so, first :

 import java.util.Arrays;

and then:

use the toString() method of Arrays class in order to return the string format of the array in your output.

 public String toString(){
    return("Book Name: " + getBookName() + 
           " chapters[] = " + Arrays.toString(getChapter()) +
           " number of chapters :  " + getNumberOfChapters());
 }

edited Dec 5, 2015 at 17:03

answered Dec 5, 2015 at 16:56

Desaretiuss

3111 gold badge3 silver badges13 bronze badges

Comments

Naruto · Accepted Answer · 2015-12-05 17:08:23Z

0

This can be achieved in many ways...

1)

Arrays.toString(chapters)

to get a nice output.

2)

You can also use:-

Arrays.asList(getChapter())

3)Instead of String[] use List...in this way...automatically toString will print it in correct format.

answered Dec 5, 2015 at 17:08

Naruto

4,3591 gold badge24 silver badges32 bronze badges

Collectives™ on Stack Overflow

Declaring an array of strings that can be directly printed Java

5 Answers 5

2 Comments

1 Comment

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

2 Comments

1 Comment

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related