就是逻辑上是二叉树，物理上是一个数组

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需求

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package tree;public class ArrayBinaryTreeDemo {public static void main(String[] args) {int arr [] = {1, 2, 3, 4, 5, 6, 7};ArrayBinaryTree arrayBinaryTree = new ArrayBinaryTree(arr);//arrayBinaryTree.preOrder();//arrayBinaryTree.infixOrder();arrayBinaryTree.postOrder();}
}
//编写一个ArrayBinaryTree，实现顺序存储二叉树
class ArrayBinaryTree{private int [] arr; //存储数据节点的数组public ArrayBinaryTree(int[] arr) {this.arr = arr;}//重载preOrder()public void preOrder(){this.preOrder(0);}//重载infixOrder()public void infixOrder(){this.infixOrder(0);}//重载postOrder()public void postOrder(){this.postOrder(0);}//编写一个方法，完成顺序存储二叉树前序遍历/**** @param index 数组下标*/public void preOrder(int index){//如果数组为空，或者arr.length = 0；if (arr == null || arr.length == 0){System.out.println("数组为空，不能遍历");return;}//输出当前元素System.out.println(arr[index]);//向左递归遍历if ( (index * 2 + 1) < arr.length){preOrder(2 * index + 1);}if ((index * 2 + 2) < arr.length){preOrder(index * 2 + 2);}}//中序遍历public void infixOrder(int index){if (arr == null || arr.length == 0){System.out.println("数组为空，不能遍历");return;}if ((index * 2 + 1) < arr.length){infixOrder(index * 2 + 1);}System.out.println(arr[index]);if ((index * 2 + 2)<arr.length){infixOrder(index * 2 + 2);}}//后序遍历public void postOrder(int index){if (arr == null || arr.length == 0){System.out.println("数组为空，不能遍历");return;}if ((index * 2 + 1) < arr.length){infixOrder(index * 2 + 1);}if ((index * 2 + 2)<arr.length){infixOrder(index * 2 + 2);}System.out.println(arr[index]);}}