package test;

import java.awt.FlowLayout;
import java.awt.GridLayout;

import javax.swing.JButton;
import javax.swing.JFrame;
class App {
    public static void main(String[] args)
    {
    int num = 15;
    GridLayout experimentLayout = new GridLayout(0, 3);

    JFrame f=new JFrame();//creating instance of JFrame

    f.setSize(400,500);//400 width and 500 height
    f.setLayout(experimentLayout);

    for(int i=1; i<=num; i++) {
    f.add(new JButton("Button "+i));
    }

    f.setVisible(true);//making the frame visible
    }
}