java - 如何找到某些参数？

Question

例如我有:

ArrayList<Student> stu = new ArrayList<Student>();
stu.add(new HighSchoolStudent("Jem", "Finch", 11, 3.4));
stu.add(new Student("Scout", "Finch", 4));
stu.add(new HighSchoolStudent("Boo", "Radley", 12, 1.7));
stu.add(new HighSchoolStudent("Atticus", "Finch", 12, 4.8));
stu.add(new Student("Patrick", "Henry", 9));
stu.add(new Student("Patrick", "Henry", 11));

ArrayList<Teacher> tea = new ArrayList<Teacher>();
tea.add(new Teacher("Betsy", "Ross", "Home Ec"));
tea.add(new Teacher("Ada", "Lovelace", "Mathematics"));
tea.add(new Teacher("Grace", "Hopper", "Computer Science"));
tea.add(new Teacher("Marie", "Curie", "Chemistry"));
tea.add(new Teacher("Dolly", "Madison", "Government"));
tea.add(new Teacher("Maya", "Angelou", "English Composition"));

School sch = new School(stu, tea);
System.out.println("\n\njust seniors: \n" + sch.getGradeLevel(12));

并且 HighSchoolStudent 和 Student 都有参数 (LastName,FirstName,GradeLevel,gpa)。我如何在另一个类中创建一个方法(getGradeLevel)，当 GradeLevel 为 12 时，它只打印 arrayList 的那部分？所以我希望输出是:

Radley, Boo
   Grade Level: 12
   ID #: 5
   GPA: 1.7
Finch, Atticus
   Grade Level: 12
   ID #: 6
   GPA: 4.8

我的学校类(class)代码是

class School
{
 public ArrayList <Student> student = new ArrayList<Student>();
 public ArrayList <Teacher> teacher = new ArrayList<Teacher>();
 public String listOfNames;
 private String gradeList;
public School()
{
}
public School(ArrayList <Student> stu, ArrayList <Teacher> tec)
{
student = stu;
teacher = tec;
}

public String getGradeLevel(int grade)
{
//Need help with this part
}




public String toString()
{//Makes a string with last, first name and subject
 listOfNames+=("\nFaculty:\n");
for (int i=0;i<teacher.size();i++)
 {
  listOfNames +=" "+teacher.get(i);
}

listOfNames+="\nStudents:\n";
for (int i=0;i<student.size();i++)
{
  listOfNames +=student.get(i)+" ";
}
return listOfNames;
}//End toString
}

Answer 1

for(Student s:stu){
  if(s.getGradeLevel()==12){
    System.out.println(s);
  }
}

此答案假设您已在 Student 类中声明了一个返回学生年级的方法 getGradeLevel()，并且您已正确重写 Student .toString().