我用composite模式写的一个二叉树的例子
1，Component 是抽象组件
Tree 和Leaf 继承Component

private String name; //树或叶子的名称
addChild(Component leftChild,Component rightChild);
//给一个树上加上一个左孩子，一个右孩子
getName(){return name;}
getTreeInfo(){} //得到树或叶子的详细信息
getLength(); //得到树的高度

2，Tree 二叉树，一个左孩子，一个右孩子

3，Leaf 是叶子节点
4，Test 是测试节点

/** Component.java **************/
package binarytree;
public abstract class Component {
private String name;
public abstract Component addChild(Component leftChild,Component rightChild);
public String getName(){return name;}
public void getTreeInfo(){}
public abstract int getLength();
}

/** Leaf.java **************/
package binarytree;
public class Leaf extends Component{
private String name;
private Component leaf=null;
public Leaf(String name) {
this.name=name;
}
public Component addChild(Component leftChild,Component rightChild){
return this;
}
public String getName(){
return name;
}
public int getLength() {
return 1;
}
public static void main(String[] args) {
}
}

/** Tree.java **************/
package binarytree;
public class Tree extends Component {
private String name;
private Component leftChild;
private Component rightChild;
public Tree(String name,Component leftChild,Component rightChild) {
this.name=name;
this.leftChild=leftChild;
this.rightChild=rightChild;
}
public Tree(String name) {
this.name=name;
this.leftChild=null;
this.rightChild=null;
}
public Component addChild(Component leftChild,Component rightChild){
this.leftChild=leftChild;
this.rightChild=rightChild;
return this;
}
public String getName(){
return name;
}
public void getTreeInfo()
//得到树或叶子的详细信息
//先打印自己的名字，再遍例左孩子，再遍例右孩子
//如果左孩子或右孩子是树，递归调用
{
System.out.println(" this trees name is "+getName());
if(this.leftChild instanceof Leaf)
{
System.out.println(getName()+"s left child is "+this.leftChild.getName()+",it is a Leaf");
}
if(this.leftChild instanceof Tree){
System.out.println(getName()+"s left child is "+this.leftChild.getName()+",it is a Tree");
this.leftChild.getTreeInfo();
}
if(this.leftChild==null)
{
System.out.println(getName()+"s left child is a null");
}
if(this.rightChild instanceof Leaf)
{
System.out.println(getName()+"s right child is "+this.rightChild.getName()+",it is a Leaf");
}
if(this.rightChild instanceof Tree) {
System.out.println(getName()+"s right child is "+this.rightChild.getName()+",it is a Tree");
this.rightChild.getTreeInfo();
}
if(this.rightChild==null)
{
System.out.println(getName()+"s right child is a null");
}
//System.out.println(getName()+"s 高度 是 "+getLength());
}
public int getLength() {
//比较左孩子或右孩子的高度，谁大，+1 返回
// 空孩子的处理
if(this.leftChild==null) {
if(this.rightChild==null)
return 1;
else
return this.rightChild.getLength()+1;
}
else {
if(this.rightChild==null) {
return this.leftChild.getLength()+1;
}
else {
if((this.leftChild.getLength())>=(this.rightChild.getLength()))
return this.leftChild.getLength()+1;
else
return this.rightChild.getLength()+1;
}
}
}
public static void main(String[] args) {
}
}

/** Test.java 测试类 **************/
package binarytree;
public class Test {

public Test() {
}
public static void main(String[] args) {
Component tree=new Tree("luopeng");
Component leaf_child=new Leaf("luopeng1");
Component right_child=new Leaf("luopeng2");
tree=tree.addChild(leaf_child,right_child);
//tree=tree.addRightChild(right_child);
tree.getTreeInfo();
Component tree1=new Tree("luopeng2");
tree1.addChild(tree,leaf_child);
tree1.getTreeInfo();
Component tree2=new Tree("luopeng3");
tree2.addChild(tree,null);
tree2.getTreeInfo();
Component tree4=new Tree("luopeng4");
tree4.addChild(null,tree);
tree4.getTreeInfo();
System.out.println(tree4.getName()+"的高度是 "+tree4.getLength());
}