如何在编程中有效停止后面代码的运行？

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

class Student {
    String id;
    String name;
    int age;
    String address;

    // 省略getter和setter方法
}

public class StudentManager {

    private static Map<String, Student> students = new HashMap<>();

    public static boolean addStudent() {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入学生学号: ");
        String id = scanner.next();

        if (students.containsKey(id)) {
            System.out.println("学号已存在，添加失败!");
            return false; // 学号重复，直接返回false
        }

        Student student = new Student();
        student.id = id;
        System.out.print("请输入学生姓名: ");
        student.name = scanner.next();
        System.out.print("请输入学生年龄: ");
        student.age = scanner.nextInt();
        System.out.print("请输入学生地址: ");
        student.address = scanner.next();

        students.put(id, student);
        System.out.println("学生信息添加成功!");
        return true; // 添加成功，返回true
    }

    public static void main(String[] args) {
        if (addStudent()) {
            // 添加成功后执行后续操作
            System.out.println("可以进行后续操作...");
        } else {
            // 添加失败，不执行后续操作
            System.out.println("程序结束");
        }
    }
}