import javax.swing.*;
import java.awt.Dimension;
import java.awt.BorderLayout;

public class JScrollPaneTest4 extends JFrame{

  public static void main(String[] args){
    JScrollPaneTest4 frame = new JScrollPaneTest4();

    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setBounds(10, 10, 300, 200);
    frame.setTitle("タイトル");
    frame.setVisible(true);
  }

  JScrollPaneTest4(){
    JTextArea textarea = new JTextArea("JTextAreaを配置");

    JScrollPane scrollpane = new JScrollPane(textarea);
    scrollpane.setPreferredSize(new Dimension(200, 120));

    JPanel panel = new JPanel();
    panel.add(scrollpane);

    getContentPane().add(panel, BorderLayout.CENTER);
  }