So sánh giữa 2 id với nhau

[Nguyen_Tuan_Khai_Kha (Nguyễn Tuấn Khải)]

Nhập student

public void input(Scanner scanner) {
        id = exceptions.integerInput(scanner, "Please input id:");
        System.out.println("Please input name:");
        name = scanner.nextLine();
        markMath = exceptions.doubleInput(scanner, "Please input mark Math:");
        markPhysic = exceptions.doubleInput(scanner, "Please input mark Physic:");
        markChemistry = exceptions.doubleInput(scanner, "Please input mark Chemistry:");

    }

Nhập student vào list

public void inputStudents(Scanner scanner) {
        do {
            System.out.println("Do you want to enter Students:");
            System.out.println("1.Input");
            System.out.println("0.Exit");
            int choose = exceptions.integerInput(scanner, "--------------");
            if (choose == 0) {
                break;
            }
            switch (choose) {
                case 1:
                    Student student = new Student();
                    student.input(scanner);
                    if (list.isEmpty()) {
                        list.add(student);
                        break;
                    } else {
                        if (student instanceof List) {
                            System.out.println("This ID already exist, please re-enter another ID");
                        } else {
                            list.add(student);
                            break;
                        }
                    }
                default:
                    System.out.println("Please choose 1 or 0");
                    break;
            }
        } while (true);
    }

Mình muốn so sánh id vừa nhập có sẵn trong list không. Nếu có thì sẽ xuất thông báo.

[library (La biblioteca)]

if (student instanceof List) {
    System.out.println("This ID already exist, please re-enter another ID");
}

---

Nếu cậu dùng Java 8+

// haven't tested code
if(list.stream().map(Student::getId).anyMatch(anotherId::equals) {

  System.out.println("This ID already exist, please re-enter another ID");
}

Hope it helps!