import javax.swing.*; import java.awt.*; public class Test { Test(){ JFrame f=new JFrame("test frame"); f.setSize(500,500); JPanel p1=new JPanel(); p1.setBackground(Color.RED); JPanel p2=new JPanel(); p2.setBackground(Color.BLUE); f.setLayout(new FlowLayout(FlowLayout.CENTER)); f.setVisible(true); f.add(p1); f.add(p2); } public static void main(String[] args) { new Test(); } }