我想比较这两个向量，这样它就会返回多少病人也是学生。我得到了main，我已经添加到histandmarks方法中，但它似乎不起作用。主要的困惑在于histandmarks方法，以及如何比较两个向量。
谢谢

import java.util.*;
public class Ex6 {

    public static int count = 0;

     public static void main(String[] a)
     {
        Vector<Patient>  P = new Vector<Patient>();
        Vector<Student>  S = new Vector<Student>();
       int i=Integer.parseInt(a[0]);
       if (i==0) {
          P.add(new Patient("Jimmy1","1","d"));
          P.add(new Patient("Jimmy2","1","d"));
          P.add(new Patient("Jimmy3","1","d"));
          P.add(new Patient("Jimmy","1","d"));
          S.add(new Student("Jimmy1","1",null) );
          S.add(new Student("Jimmy2","1",null) );
          S.add(new Student("Jimmy3","1",null) );
          S.add(new Student("Lisa","1",null) );
          System.out.println(new Ex6().HistAndMarks(P,S));
        }
         if (i==1) {
          P.add(new Patient("Jimmy","1","d"));
          S.add(new Student("Jimmy1","1",null) );
           System.out.println(new Ex6().HistAndMarks(P,S));
        }
        if (i==2)  System.out.println(new Ex6().HistAndMarks(P,null));
    }

     public static int HistAndMarks (Vector<Patient>  P, Vector<Student>  S) {

        for(int i = 0; i > P.size(); i++){
            for(int z = -1; z > S.size(); z++){
                Patient Pnew = P.get(i);
                Student Snew = S.get(z + 1);
                if(P.contains(S)){
                    count = count + 1;

                }
            }
        }
       return count;
    }
}