How to keep JTree always fix to location(0,0) for its MotherPanel??

Question

Dear Friends:
I have following code,
AnimalTree.java is a JTree, AnimalTreeCall.java is a MotherPanel to add AnimalTree to it,
after I run it, it is not located at (0,0) location in AnimalTreeCall, after I resize AnimalTreeCall, AnimalTree's location will change with the size change of AnimalTreeCall.
But what I want is that
[1]. never mind how I change the size of AnimalTreeCall, AnimalTree will always fix to the location of (0,0) in AnimalTreeCall Panel,ie. fix to upper left corner;
and
[2]. AnimalTree JTree will occupy all area in AnimalTreeCall, not only part of it
How to do that??
Thanks
1. AnimalTreeCall.java
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.*;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JSplitPane;
import java.awt.GridLayout;
public class AnimalTreeCall {
     private static final long serialVersionUID = 1L;
     private           static JFrame                     frame;
     protected           static AnimalTree     animalTree ;
     private               JSplitPane sp = new JSplitPane();     
     public static void main(String args[]) {
          animalTree = new AnimalTree();
          animalTree.init();
          JScrollPane jp= new JScrollPane();
          animalTree.setPreferredSize(new Dimension(600,600));
         jp.setPreferredSize(new Dimension(600,600));
         AnimalTreeCall tc = new AnimalTreeCall();
          frame = new JFrame("test");
          frame.setBounds(0, 0, 600, 675);
          frame.setPreferredSize(new Dimension(600,600));
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         jp.setViewportView(animalTree);
          frame.add(tc.showGUI(), BorderLayout.NORTH);
          frame.add(jp, BorderLayout.CENTER);
          frame.addWindowListener(new WindowAdapter() {
                 public void windowClosing(WindowEvent e) {
                     System.exit(0);
             frame.pack();
             frame.setVisible(true);
     public JPanel showGUI() {
             JPanel jp = new JPanel();
             jp.setLayout(new GridLayout(0,30));            
             jp.setSize(15,15);
             jp.setBorder(BorderFactory.createLineBorder(Color.white));
                 return jp;
}2. AnimalTree.java
import java.awt.BorderLayout;
import java.awt.Dimension;
import javax.swing.*;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
public class AnimalTree extends JPanel{
     private static final long serialVersionUID = 1L;
    protected           JTree                               tree;
    protected           DefaultTreeModel                model;
    protected           DefaultMutableTreeNode           rootNode;
     public AnimalTree(){
          super();
     public void init() {
         DefaultMutableTreeNode ProjectNode = getProjectTree();
         model      = new DefaultTreeModel(ProjectNode);
         tree      = new JTree(model);
         tree.setPreferredSize(new Dimension(400,300));
         add(tree, new BorderLayout().CENTER);
  private DefaultMutableTreeNode getProjectTree() {
    rootNode = new DefaultMutableTreeNode("Root");
    DefaultMutableTreeNode an = new DefaultMutableTreeNode("Animal");
    rootNode.add(an);
    DefaultMutableTreeNode cat = new DefaultMutableTreeNode("Cat");
    an.add(cat);
    DefaultMutableTreeNode t = new DefaultMutableTreeNode("Tiger");
    an.add(t);  
    DefaultMutableTreeNode shark = new DefaultMutableTreeNode("Shark");
    an.add(shark);  
    DefaultMutableTreeNode p = new DefaultMutableTreeNode("Pig");
    an.add(p);  
    DefaultMutableTreeNode dog = new DefaultMutableTreeNode("Dog");
    an.add(dog);  
    DefaultMutableTreeNode bird = new DefaultMutableTreeNode("Bird");
    p.add(bird);
    DefaultMutableTreeNode hawk = new DefaultMutableTreeNode("Hawk");
    p.add(hawk);
    DefaultMutableTreeNode eagle = new DefaultMutableTreeNode("Eagle");
    p.add(eagle);
    DefaultMutableTreeNode sp = new DefaultMutableTreeNode("Sparraw");
    p.add(sp);
    DefaultMutableTreeNode mouse = new DefaultMutableTreeNode("Mouse");
    p.add(mouse);
    return rootNode;
}

Answer 1

Use the appropriate LayoutManager. Start by reading the Swing tutorial. I'm sure you've been given the link to the tutorial many time.
add(tree, new BorderLayout().CENTER);The above statement makes no sense.
I suggest you use a System.out.println(...) to see what the default layout manager for a JPanel is.