Creating a method to print ArrayList, then calling it in another class

问题

I've built an Arraylist in My class 'BookList', but I need it to print in another class.

I think I may have to turn the printing of an Arraylist into a method, so then it can be called from a different class; if I am wrong though, what else could I do to accomplish this?

Below is my code, for reference.

import java.util.ArrayList;


public class BookList {

public static void main (String[] args){

    Book a = new Book();

    a.setTitle("Random ");
    a.setAuthor("Craig Robertson");
    a.setBookID("1847398812");
    a.setonLoan(false);
    a.setNumberofLoans(3);

    Book b = new Book();

    b.setTitle("The Last Refuge");
    b.setAuthor("Craig Robertson");
    b.setBookID("1471127753");
    b.setonLoan(false);
    b.setNumberofLoans(2);

    Book c = new Book();

    c.setTitle("The Bird That Did Not Sing");
    c.setAuthor("Alex Gray");
    c.setBookID("0751548278");
    c.setonLoan(true);
    c.setNumberofLoans(7);

    ArrayList<Book> BookList = new ArrayList<Book>();
    BookList.add(a);
    BookList.add(b);
    BookList.add(c);

    int count = BookList.size();
    System.out.println("Count: " + count);
    System.out.println("");

        for (Book  d : BookList){
            System.out.println(d);

    }   
  }
}

To go with this, I have the toString() method in my 'Book' class, so I could print all objects.

An additional question: How would I print just the title and author of each object?

回答1:

Create a static method in your Book class that will handle the display:

public static void showBooks(ArrayList<Book> books) {
    for (Book  d : Books){
        System.out.println(d); // calls the 'toString' method on each Book object
}

And call it this way from the main method:

ArrayList<Book> BookList = new ArrayList<Book>();
BookList.add(a);
BookList.add(b);
BookList.add(c);

Book.showBooks(BookList); // prints the books, one by one

How would I print just the title and author of each object?

You can choose to print the title and author only in the overriden toString method of your Book class:

@Override
public String toString() {
    // 'author' & 'title' are members of the 'Book' class
    return "Author: " + author + "- Title: " + title;
}

回答2:

Override the BookList tostring method like so :

public class BookList{
    @Override
    public String toString(){
        // Return some string here
    }
}

Then just use it normally.

System.out.println(myBookList);

来源：https://stackoverflow.com/questions/34192644/creating-a-method-to-print-arraylist-then-calling-it-in-another-class

标签

java

arraylist