public class Book {
    private String author;
    private String bookName;
    private int bookPrice;
}

import java.util.List;
import java.util.ArrayList;
class Book
{
    private String author;
    private String bookName;
    private int bookPrice;
    public Book(String author,String bookName,int bookPrice)
    {
        this.author=author;
        this.bookName=bookName;
        this.bookPrice=bookPrice;
    }
    public String getAuthor()
    {
        return this.author;
    }
    public String getBookName()
    {
        return this.bookName;
    }
    public int getBookPrice()
    {
        return this.bookPrice;
    }
}
public class BookTest
{
    public static void main(String[] args)
    {
        List<Book> list=new ArrayList<Book>();
        list.add(new Book("张三","书名1",100));
        list.add(new Book("李四","书名2",110));
        list.add(new Book("王五","书名3",120));        
        String[][] child=new String[list.size()][3];        
        for(int i=0;i<child.length;i++)
        {
            for(int j=0;j<3;j++)
            {
                child[j][0]=list.get(j).getAuthor();
                child[j][1]=list.get(j).getBookName();
                child[j][2]=String.valueOf(list.get(j).getBookPrice());
            }
        }        
        for(String[] test:child)
            for(String s:test)
                System.out.print(s+" ");
    }
}

------解决方案--------------------
for (int i = 0; i < books.size(); i++) {
Book book = books.get(i);
child[i][0] = book.getAuthor();
child[i][1] = book.getBookName();
child[i][2] = book.getBookPrice() + "";
}

对的，主要就是这个for循环。