public class PlayCards { public static void main(String[] args) { String[] color = {"黑桃", "梅花", "方片", "红桃"}; String[] num = {"A", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K"}; ArrayList<String> cards = new ArrayList<>(); //洗牌 for (int i = 0; i < color.length; i ) { for (int j = 0; j < num.length; j ) { cards.add(color[i] num[j]); } } cards.add("大王"); cards.add("小王"); Collections.shuffle(cards); ArrayList<String> 林志玲 = new ArrayList<>(); ArrayList<String> 林心如 = new ArrayList<>(); ArrayList<String> 舒淇 = new ArrayList<>(); //留下3张底牌 for (int i = 0; i < cards.size() - 3; i ) { if (i % 3 == 0) { 林志玲.add(cards.get(i)); } else if (i % 3 == 1) { 林心如.add(cards.get(i)); } else if (i % 3 == 2) { 舒淇.add(cards.get(i)); } } System.out.println("林志玲：" 林志玲); System.out.println("林心如：" 林心如); System.out.println("舒淇：" 舒淇); System.out.println("底牌："); for (int i = cards.size() - 3; i < cards.size(); i ) { System.out.println(cards.get(i)); } }}先在项目的根目录下创建 student.txt,用户存储用户输入的信息。学生类: public class Student { private String id; private String name; private String age; private String address; // 空参和有参构造方法 // getter、setter方法 }系统程序: public class StudentManagerIO { public static void main(String[] args) throws IOException { String fileName = "student.txt"; //为了使主程序回到这里，使用循环 while (true) { //学生管理系统主界面 System.out.println("----------欢迎来到学生管理系统----------"); System.out.println("1 查看所有学生"); System.out.println("2 添加学生"); System.out.println("3 删除学生"); System.out.println("4 修改学生"); System.out.println("5 退出系统"); System.out.println("请输入你的选择："); //创建键盘录入对象 Scanner scanner = new Scanner(System.in); String choiceString = scanner.nextLine(); //使用 Switch语句 switch (choiceString) { case "1": //查看所有学生 findAllStudent(fileName); break; case "2": //添加学生 addStudent(fileName); break; case "3": //删除学生 deleteStudent(fileName); break; case "4": //修改学生 updateStudent(fileName); break; case "5": //退出 System.out.println("谢谢你的使用"); System.exit(0); //JVM退出 default: System.out.println("你的输入有误，请重新选择"); } } } //从文件中读取数据到集合 private static void readData(String fileName, ArrayList<Student> array) throws IOException { BufferedReader reader = new BufferedReader(new FileReader(fileName)); String line; while ((line = reader.readLine()) != null) { String[] datas = line.split(","); Student student = new Student(); student.setId(datas[0]); student.setName(datas[1]); student.setAddress(datas[2]); student.setAddress(datas[3]); array.add(student); } reader.close(); } //把集合中的数据写入文件 private static void writeData(String fileName, ArrayList<Student> array) throws IOException { BufferedWriter writer = new BufferedWriter(new FileWriter(fileName)); for (int i = 0; i < array.size(); i ) { Student student = array.get(i); StringBuffer sb = new StringBuffer(); sb.append(student.getId()).append(",").append(student.getName()).append(",") .append(student.getAge()).append(",").append(student.getAddress()); writer.write(sb.toString()); writer.newLine(); writer.flush(); } writer.close(); } //修改学生 public static void updateStudent(String fileName) throws IOException { ArrayList<Student> array = new ArrayList<>(); readData(fileName, array); Scanner sc = new Scanner(System.in); System.out.println("请输入你要修改的学生的学号："); String id = sc.nextLine(); int index = -1; for (int i = 0; i < array.size(); i ) { Student student = array.get(i); if (student.getId().equals(id)) { index = i; break; } } if (index == -1) { System.out.println("不好意思,你要修改的学号对应的学生信息不存在,请回去重新你的选择"); } else { System.out.println("请输入学生新姓名："); String name = sc.nextLine(); System.out.println("请输入学生新年龄："); String age = sc.nextLine(); System.out.println("请输入学生新居住地："); String address = sc.nextLine(); Student student = new Student(); student.setId(id); student.setName(name); student.setAge(age); student.setAddress(address); array.set(index, student); writeData(fileName, array); System.out.println("修改成功！！！"); } } //删除学生 public static void deleteStudent(String fileName) throws IOException { ArrayList<Student> array = new ArrayList<>(); readData(fileName, array); Scanner scanner = new Scanner(System.in); System.out.println("请输入需要删除的学生学号："); String id = scanner.nextLine(); int index = -1; for (int i = 0; i < array.size(); i ) { Student student = array.get(i); if (student.getId().equals(id)) { index = i; break; } } if (index == -1) { System.out.println("不好意思，你要删除的学生信息不存在，请重新选择"); } else { array.remove(index); writeData(fileName, array); System.out.println("删除成功！！"); } } //添加学生信息 public static void addStudent(String fileName) throws IOException { ArrayList<Student> array = new ArrayList<>(); //从文件中读取数据到集合 readData(fileName, array); Scanner scanner = new Scanner(System.in); String id; while (true) { System.out.println("请输入学生学号："); id = scanner.nextLine(); //判断学号是否被占用 boolean flag = isExist(array, id); if (flag) { System.out.println("对不起，你输入的学号被占用，请重新输入"); } else { break; } } System.out.println("请输入学生姓名："); String name = scanner.nextLine(); System.out.println("请输入学生年龄："); String age = scanner.nextLine(); System.out.println("请输入学生住址："); String address = scanner.nextLine(); Student student = new Student(); student.setId(id); student.setName(name); student.setAge(age); student.setAddress(address); array.add(student); writeData(fileName, array); System.out.println("添加成功！！"); } //判断学号是否被占用 private static boolean isExist(List<Student> array, String id) { for (int i = 0; i < array.size(); i ) { Student student = array.get(i); if (student.getId().equals(id)) { return true; } } return false; } //查看所有学生 public static void findAllStudent(String fileName) throws IOException { ArrayList<Student> array = new ArrayList<>(); readData(fileName, array); if (array.size() == 0) { System.out.println("不好意思，暂时没有学生信息可供查询，请重新选择"); return; } System.out.println("学号\t姓名\t年龄\t居住地"); array.forEach(student -> System.out.println(student.getId() "\t" student.getName() "\t" student.getAddress() "\t" student.getAddress() ) ); } }联系客服
