Java学习(十八)：二叉树的三种递归遍历

二叉树的三种递归遍历：

public class StudentNode
{
    private String name;
    
    private StudentNode leftNode;
    
    private StudentNode rightNode;
    
    public String getName()
    {
        return name;
    }
    
    public void setName(String name)
    {
        this.name = name;
    }
    
    public StudentNode getLeftNode()
    {
        return leftNode;
    }
    
    public void setLeftNode(StudentNode leftNode)
    {
        this.leftNode = leftNode;
    }
    
    public StudentNode getRightNode()
    {
        return rightNode;
    }
    
    public void setRightNode(StudentNode rightNode)
    {
        this.rightNode = rightNode;
    }
    
    public static void main(String[] args)
    {
        StudentNode root = new StudentNode();
        root.setName("Name1");
        StudentNode node2 = new StudentNode();
        node2.setName("Name2");
        StudentNode node3 = new StudentNode();
        node3.setName("Name3");
        StudentNode node4 = new StudentNode();
        node4.setName("Name4");
        StudentNode node5 = new StudentNode();
        node5.setName("Name5");
        StudentNode node6 = new StudentNode();
        node6.setName("Name6");
        StudentNode node7 = new StudentNode();
        node7.setName("Name7");
        //
        // ****root***
        // ***/ *****
        // **2 ****5**
        // */  **/***
        // 3 *4 **6***
        // **********
        // ********7**
        //
        root.setLeftNode(node2);
        root.setRightNode(node5);
        node2.setLeftNode(node3);
        node2.setRightNode(node4);
        node5.setLeftNode(node6);
        node6.setRightNode(node7);
        
        // 前序遍历1-2-3-4-5-6-7
        rootFirst(root);
        // 中序遍历3-2-4-1-6-7-5
        rootMiddle(root);
        // 后序遍历3-4-2-7-6-5-1
        rootLast(root);
    }
    
    private static void rootFirst(StudentNode node)
    {
        System.out.println(node.getName());
        if (null != node.getLeftNode())
        {
            rootFirst(node.getLeftNode());
        }
        if (null != node.getRightNode())
        {
            rootFirst(node.getRightNode());
        }
    }
    
    private static void rootMiddle(StudentNode node)
    {
        if (null != node.getLeftNode())
        {
            rootMiddle(node.getLeftNode());
        }
        System.out.println(node.getName());
        if (null != node.getRightNode())
        {
            rootMiddle(node.getRightNode());
        }
    }
    
    private static void rootLast(StudentNode node)
    {
        if (null != node.getLeftNode())
        {
            rootLast(node.getLeftNode());
        }
        if (null != node.getRightNode())
        {
            rootLast(node.getRightNode());
        }
        System.out.println(node.getName());
    }
}