如何将System.out.print从函数显示到JOptionPane.showMessageDialog？

Question

How can I display the something like following using JOptionPane.showMessageDialog? I've tried using with String.format but that doesn't appear to work or I'm either doing it incorrectly.

public void Display ()
{
    int size_ = rows_ * columns_;
    for (int i = 1; i <= size_; ++i)
    {
        System.out.print( "* ");
        if (i % columns_ == 0)
        {
            System.out.print( "\n ");
        }
    }
}

Answer 1

Use StringBuilder to build the desired String(using append() ). The you can simply call toString() on the StringBuilder instance to get the String and use it in your JOptionPane.showMessageDialog() method.