java 带滚动条的多行文本输入

package test;

import java.awt.GridLayout;
import java.awt.LayoutManager;
//import java.util.EmptyStackException;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

public class test {
    public static void main(String[] args) {
        JFrame f = new JFrame("Welcome To Earth!");
        JTextArea jt = new JTextArea(3, 20);
        jt.setLineWrap(true);// 如果内容过长。自动换行

        JScrollPane scr = new JScrollPane(jt,
                JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
                JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
        // lab.setBounds(10, 10, 120, 20);
// jt.setBounds(130, 10, 150, 100);
        JLabel lab = new JLabel("多行输入文本:");

        f.setLayout(new GridLayout(2, 1));
        
        f.add(lab);
        f.add(scr);
        // f.add(jt);
        f.setSize(300, 150);
        f.setLocation(300, 200);
        f.setVisible(true);

    }

}