2.5.1.1 语法结构

public void 方法名(类名<?> 参数名)

举例：

public class Student<T> {
    private T flag;
    public T getFlag() {
        return flag;
    }
    public void setFlag(T flag) {
        this.flag = flag;
    }
}

public class Student_1 {
    public void showFlag(Student<?> flag){
        System.out.println(flag.getFlag());
    }
}

public class Test_3 {
    public static void main(String[] args) {
        Student_1 student_1 = new Student_1();
        Student<Integer> student = new Student<>();
        student.setFlag(20);
        student_1.showFlag(student);
        Student<String> student1 = new Student<>();
        student1.setFlag("爱摸鱼的TT~");
        student_1.showFlag(student1);
    }
}