实现线性表的插入、删除、求表长、查找给定值 e、查找第 i 个位置元素 等基本操作，要求编写的程序以菜单方式工作

要实现一个简单的线性表（如数组或链表）的基本操作，你可以使用Java编写一个命令行界面的程序。这里我会给出一个基于数组实现的简单示例，包括插入、删除、求表长、查找和显示元素等操作。我们将使用一个`ArrayList`来存储数据，因为它的大小可变并且提供了方便的方法进行这些操作。

import java.util.ArrayList;
import java.util.Scanner;

class LinearList {
    private ArrayList<Integer> list;

    public LinearList() {
        list = new ArrayList<>();
    }

    // 插入元素
    public void insert(int value, int position) {
        if (position >= 0 && position <= list.size()) {
            list.add(position, value);
        } else {
            System.out.println("Invalid position.");
        }
    }

    // 删除元素
    public void delete(int position) {
        if (position >= 0 && position < list.size()) {
            list.remove(position);
        } else {
            System.out.println("Invalid position.");
        }
    }

    // 求表长
    public int length() {
        return list.size();
    }

    // 查找元素
    public boolean search(int value) {
        return list.contains(value);
    }

    // 查找第i个元素
    public int get(int index) {
        if (index >= 0 && index < list.size()) {
            return list.get(index);
        } else {
            System.out.println("Invalid index.");
            return -1; // 返回默认值或者抛异常取决于需求
        }
    }

    // 显示列表元素
    public void display() {
        System.out.print("Linear List: ");
        for (int i : list) {
            System.out.print(i + " ");
        }
        System.out.println();
    }
}

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        LinearList linearList = new LinearList();

        while (true) {
            System.out.println("\n1. Insert");
            System.out.println("2. Delete");
            System.out.println("3. Check Length");
            System.out.println("4. Search");
            System.out.println("5. Get Element by Index");
            System.out.println("6. Display");
            System.out.println("7. Exit");

            System.out.print("Enter your choice: ");
            int choice = scanner.nextInt();

            switch (choice) {
                case 1:
                    System.out.print("Position and Value: ");
                    int pos = scanner.nextInt(), val = scanner.nextInt();
                    linearList.insert(val, pos);
                    break;
                case 2:
                    System.out.print("Position to delete: ");
                    pos = scanner.nextInt();
                    linearList.delete(pos);
                    break;
                case 3:
                    System.out.println("Length of the list: " + linearList.length());
                    break;
                case 4:
                    System.out.print("Value to search: ");
                    int searchVal = scanner.nextInt();
                    boolean found = linearList.search(searchVal);
                    if (found) {
                        System.out.println("Found");
                    } else {
                        System.out.println("Not Found");
                    }
                    break;
                case 5:
                    System.out.print("Index: ");
                    int idx = scanner.nextInt();
                    int element = linearList.get(idx);
                    if (element != -1) {
                        System.out.println("Element at index " + idx + ": " + element);
                    }
                    break;
                case 6:
                    linearList.display();
                    break;
                case 7:
                    System.out.println("Exiting...");
                    scanner.close();
                    return;
                default:
                    System.out.println("Invalid choice. Please try again.");
            }
        }
    }
}

这个程序提供了一个简单的菜单，用户可以根据指示执行相应的操作。你可以根据需要修改和扩展这个程序，比如添加错误处理或优化用户体验。如果你对其他数据结构（如链表）有兴趣，可以替换`ArrayList`为`LinkedList`并相应地调整方法实现。