java代码实现创建一棵二叉链表表示的二叉树中，实现以广义表表示构造二叉树,并采用先根、中根、后根、层次算法输出二叉树字符

可以参考以下 Java 代码实现：

import java.util.LinkedList;
import java.util.Queue;

class TreeNode {
    char val;
    TreeNode left;
    TreeNode right;

    TreeNode(char x) {
        val = x;
    }
}

public class BinaryTree {
    public static void main(String[] args) {
        String str = "A(B(D,E(G,)),C(,F))"; // 广义表表示的二叉树
        TreeNode root = createBinaryTree(str);
        System.out.println("先根遍历：");
        preOrder(root);
        System.out.println();
        System.out.println("中根遍历：");
        inOrder(root);
        System.out.println();
        System.out.println("后根遍历：");
        postOrder(root);
        System.out.println();
        System.out.println("层次遍历：");
        levelOrder(root);
    }

    // 创建二叉树
    public static TreeNode createBinaryTree(String str) {
        if (str == null || str.length() == 0) {
            return null;
        }
        TreeNode root = null;
        int i = 0;
        int len = str.length();
        char[] chars = str.toCharArray();
        Queue<TreeNode> queue = new LinkedList<>();
        while (i < len) {
            char ch = chars[i];
            if (ch == '(') {
                queue.offer(root);
            } else if (ch == ')') {
                queue.poll();
            } else {
                TreeNode node = new TreeNode(ch);
                if (root == null) {
                    root = node;
                } else {
                    TreeNode parent = queue.peek();
                    if (parent.left == null) {
                        parent.left = node;
                    } else {
                        parent.right = node;
                    }
                }
                queue.offer(node);
            }
            i++;
        }
        return root;
    }

    // 先根遍历
    public static void preOrder(TreeNode root) {
        if (root != null) {
            System.out.print(root.val + " ");
            preOrder(root.left);
            preOrder(root.right);
        }
    }

    // 中根遍历
    public static void inOrder(TreeNode root) {
        if (root != null) {
            inOrder(root.left);
            System.out.print(root.val + " ");
            inOrder(root.right);
        }
    }

    // 后根遍历
    public static void postOrder(TreeNode root) {
        if (root != null) {
            postOrder(root.left);
            postOrder(root.right);
            System.out.print(root.val + " ");
        }
    }

    // 层次遍历
    public static void levelOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            TreeNode node = queue.poll();
            System.out.print(node.val + " ");
            if (node.left != null) {
                queue.offer(node.left);
            }
            if (node.right != null) {
                queue.offer(node.right);
            }
        }
    }
}

其中，`createBinaryTree` 方法使用队列实现广义表表示的二叉树的构造，`preOrder`、`inOrder`、`postOrder` 和 `levelOrder` 分别实现了先根、中根、后根和层次遍历算法，可以根据需要调用。