关于GridBagLayout的有关问题，请问

import java.awt.*;import java.awt.event.*;public class GridBagLayoutDemo extends Frame{    Label l1,l2,l3,l4;    TextField tf1,tf2,tf3;    Button btn1,btn2;    CheckboxGroup cbg;    Checkbox cb1,cb2,cb3,cb4;    GridBagLayout gb;    GridBagConstraints gbc;    public GridBagLayoutDemo(String title) {        super(title);        l1=new Label("Name:");        l2=new Label("Password:");        l3=new Label("Repeate:");        l4=new Label("tujing:");        tf1=new TextField(20);        tf2=new TextField(20);        tf3=new TextField(20);        gb=new GridBagLayout();        setLayout(gb);        gbc=new GridBagConstraints();        Panel p=new Panel();        cbg=new CheckboxGroup();        cb1=new Checkbox("Search",cbg,false);        cb2=new Checkbox("Advertise",cbg,false);        cb3=new Checkbox("Friends",cbg,false);        cb4=new Checkbox("Others",cbg,false);        p.add(cb1);        p.add(cb2);        p.add(cb3);        p.add(cb4);        btn1=new Button("Submit");        btn2=new Button("Reset");        Panel p1=new Panel();        p1.add(btn1);        p1.add(btn2);        addWindowListener(new WindowAdapter() {            public void windowClosing(WindowEvent we) {                System.exit(0);            }        });        gbc.fill=GridBagConstraints.HORIZONTAL;        addComponent(l1,0,0,1,1);        addComponent(tf1,0,2,1,4);        addComponent(l2,1,0,1,1);        addComponent(tf2,1,2,1,4);        addComponent(l3,2,0,1,1);        addComponent(tf3,2,2,1,4);        addComponent(l4,3,0,1,1);        addComponent(p,3,2,1,1);        addComponent(p1,4,2,1,5);    }        public void addComponent(Component c,int row,int col,int nrow,int ncol) {        gbc.gridx=col;        gbc.gridy=row;        gbc.gridheight=ncol;        gbc.gridwidth=nrow;        gb.setConstraints(c, gbc);        add(c);    }        public static void main(String[] args) {        GridBagLayoutDemo mygb=new GridBagLayoutDemo("GridBagLayout");        mygb.setSize(500,400);        mygb.setVisible(true);    }}

import java.awt.Button;import java.awt.Checkbox;import java.awt.CheckboxGroup;import java.awt.Component;import java.awt.Frame;import java.awt.GridBagConstraints;import java.awt.GridBagLayout;import java.awt.Label;import java.awt.Panel;import java.awt.TextField;import java.awt.event.WindowAdapter;import java.awt.event.WindowEvent;public class GridBagLayoutDemo extends Frame{    Label l1,l2,l3,l4;    TextField tf1,tf2,tf3;    Button btn1,btn2;    CheckboxGroup cbg;    Checkbox cb1,cb2,cb3,cb4;    GridBagLayout gb;    GridBagConstraints gbc;    public GridBagLayoutDemo(String title) {        super(title);        l1=new Label("Name:");        l2=new Label("Password:");        l3=new Label("Repeate:");        l4=new Label("tujing:");        tf1=new TextField(20);        tf2=new TextField(20);        tf3=new TextField(20);        gb=new GridBagLayout();        setLayout(gb);        gbc=new GridBagConstraints();        Panel p=new Panel();        cbg=new CheckboxGroup();        cb1=new Checkbox("Search",cbg,false);        cb2=new Checkbox("Advertise",cbg,false);        cb3=new Checkbox("Friends",cbg,false);        cb4=new Checkbox("Others",cbg,false);        p.add(cb1);        p.add(cb2);        p.add(cb3);        p.add(cb4);        btn1=new Button("Submit");        btn2=new Button("Reset");        Panel p1=new Panel();        p1.add(btn1);        p1.add(btn2);        addWindowListener(new WindowAdapter() {            public void windowClosing(WindowEvent we) {                System.exit(0);            }        });        gbc.fill=GridBagConstraints.HORIZONTAL;        addComponent(l1,0,0,1,1);        addComponent(tf1,0,2,1,4);        addComponent(l2,1,0,1,1);        addComponent(tf2,1,2,1,4);        addComponent(l3,2,0,1,1);        addComponent(tf3,2,2,1,4);        addComponent(l4,3,0,1,1);        addComponent(p,3,2,1,1);        addComponent(p1,4,2,1,5);    }        public void addComponent(Component c,int row,int col,int nrow,int ncol) {        gbc.gridx=col;        gbc.gridy=row;                // gridheight、gridwidth颠倒了        // gbc.gridheight=ncol;        // gbc.gridwidth=nrow;                gbc.gridheight=nrow;        gbc.gridwidth=ncol;                gb.setConstraints(c, gbc);        add(c);    }        public static void main(String[] args) {        GridBagLayoutDemo mygb=new GridBagLayoutDemo("GridBagLayout");        mygb.setSize(500,400);        mygb.setVisible(true);    }}