Написание функции для добавления записи и функции для удаления записи из arraylist в Java

Question

Мне нужно сделать функцию, чтобы добавить новых учеников в arraylist и функцию, чтобы удалить студентов из arraylist, используя их идентификатор студента. Любая помощь будет принята с благодарностью! Эта проблема уже решена.

public class Main { 

public static void main(String[] args) throws Exception { 
    String stdID; 
    int tScore1; 
    int tScore2; 
    int tScore3; 
    String sName; 
    Students workobj; 

    try{ 
     //opening the file for input 
     FileInputStream istream = new FileInputStream("input.txt"); 
     Scanner input = new Scanner(istream); 
     //creating an arraylist to store student objects 
     ArrayList<Students> AllStudents= new ArrayList<Students>(); 

     while(input.hasNextLine()){ 


      stdID=input.next(); 



      sName=input.next(); 



      tScore1=input.nextInt(); 

      tScore2=input.nextInt(); 

      tScore3=input.nextInt(); 






      Students StudentRecord= new Students(stdID,sName,tScore1,tScore2,tScore3); 
      StudentRecord.listStudents(); 
      AllStudents.add(StudentRecord); 
     } 

     for(int i=0;i<=AllStudents.size()-1;i++){ 

      workobj=AllStudents.get(i); 
      workobj.listStudents(); 
     } 
     deleteStudent("99I9"); 

     sortLarge(AllStudents); 
     for(int i=0; i<=AllStudents.size()-1;i++){ 
      workobj=AllStudents.get(i); 
      workobj.listStudents(); 
     } 

    } 

     catch (FileNotFoundException e){ 
      System.out.println("file not found"); 
      System.err.println("File not found"); 
      System.exit(11); 
    } 
      catch (InputMismatchException e){ 
       System.out.println("Error in Reading File"); 
       System.err.println("Error in Reading File"); 
       System.exit(10); 
      } 
    finally { 
     output.close(); 
     System.exit(2); 
    } 
} 
    public static class Students{ 

     String studentID; 
     String Name; 
     int TestScore01; 
     int TestScore02; 
     int TestScore03; 
     double tAvg; 
     String tGrade; 

     public Students(String stdID, String sName, int tScore1,int tScore2, int tScore3){ 
      studentID=stdID; 
      Name=sName; 
      TestScore01=tScore1; 
      TestScore02=tScore2; 
      TestScore03=tScore3; 

      tAvg = ((tScore1+ tScore2 + tScore3)/300.0)*100; 


     } 
     public void listStudents(){ 
      //this function lists all of the elements of the student 
      System.out.println("\nNew Student\n Student ID: "+studentID); 
      System.out.println(" Student Name: "+ Name); 
      System.out.println(" Test 1 Score: " + TestScore01); 
      System.out.println(" Test 2 Score: " +TestScore02); 
      System.out.println(" Test 2 Score:" + TestScore03); 
      System.out.println(" Average Test Score " +tAvg); 
      System.out.println(" Grade: " + tGrade); 
     }//end of listStudents() 
     public int compareTo(Object o){ 
      //this functions compares the average test score of two students 
      if (gettAvg()<((Students)o).gettAvg()) return 1; 
      else 
       if(gettAvg()>((Students)o).gettAvg())return-1; 
        else return 0; 
     } 

     } 
    } 
public static void sortLarge(ArrayList<Students>mylist){ 
    Students xsave, ysave; 
    int isw=1, xlast=mylist.size(); 
     while (isw==1){isw=0; 
      for (int i=0;i<=xlast-2;i++){ 
       if (((mylist.get(i)).compareTo((mylist.get(i+1)))==1)){ 
        xsave=mylist.get(i); 
        ysave=mylist.get(i+1); 
        mylist.remove(i); 
        mylist.add(i,ysave); 
        mylist.remove(i+1); 
        mylist.add(i+1,xsave); 
        isw=1; 
       } 
      } 
     } 
    return; 
} 
} 

Answer 1

Я не сильно изменился. Теперь есть методы добавления/удаления. Обратите внимание: карта может быть лучше, чем ArrayList. Попробуйте попробовать и посмотрите, поможет ли вам это.

public class Students { 

    static ArrayList<Student> AllStudents= new ArrayList<Student>(); 

    public static void main(String[] args) throws Exception { 
     String stdID; 
     int tScore1; 
     int tScore2; 
     int tScore3; 
     String sName; 
     String fName; 
     String lName; 
     String wName; 
     Student workobj; 
     //****************************************External Output***************************************************** 
     PrintWriter output; 
     output=new PrintWriter(new File("StudentOut.txt")); 
     //****************************************External Input****************************************************** 
     try{ 
      //opening the file for input 
      FileInputStream istream = new FileInputStream("input.txt"); 
      Scanner input = new Scanner(istream); 
       //creating an arraylist to store student objects 
      while(input.hasNextLine()) { 

       //first I will read the student id 
       stdID=input.next(); 

       //next I will read the student name 
       fName= input.next(); 
       lName=input.next(); 
       if (input.hasNextInt()){ 
        wName=""; 
       }else{ 
        wName=input.next(); 
       } 
       sName=fName+" " +lName+" "+wName; 

       //next read in the test scores 
       tScore1=input.nextInt(); 
       tScore2=input.nextInt(); 
       tScore3=input.nextInt(); 

       //creating a student object 
       Student StudentRecord= new Student(stdID,sName,tScore1,tScore2,tScore3); 
       StudentRecord.listStudents(); 
       //now store this in allstudents 
       addStudent(AllStudents, StudentRecord); 
      }//end of while 
      //Now I will list the records 

      System.out.println("Getting Students from AllStudents Container"); 
      for(int i=0;i<=AllStudents.size()-1;i++){ 
       //retrieving the object 
       workobj=AllStudents.get(i); 
       workobj.listStudents(); 
      }//end of for 

      System.out.println("Size prior to deleting="+AllStudents.size()); 
      deleteStudent(AllStudents, "99I9"); 
      System.out.println("Size after deleting="+AllStudents.size()); 

      System.out.println("This is the sorted values of Students from the AllStudents container"); 
      sortLarge(AllStudents); 
      for(int i=0; i<=AllStudents.size()-1;i++){ 
       workobj=AllStudents.get(i); 
       workobj.listStudents(); 
      } 

     }//end of try 

      catch (FileNotFoundException e){ 
       System.out.println("file not found"); 
       System.err.println("File not found"); 
       System.exit(11); 
     }// end catch 
       catch (InputMismatchException e){ 
        System.out.println("Error in Reading File"); 
        System.err.println("Error in Reading File"); 
        System.exit(10); 
       } 
     finally { 
      output.close(); 
      System.exit(2); 
     } 
    }//end of main 

    static class Student { 
     //This is the student class object. It calculates the test average, and finds the grade 
     String studentID; 
     String Name; 
     int TestScore01; 
     int TestScore02; 
     int TestScore03; 
     double tAvg; 
     String tGrade; 

     public Student(String stdID, String sName, int tScore1,int tScore2, int tScore3){ 
      studentID=stdID; 
      Name=sName; 
      TestScore01=tScore1; 
      TestScore02=tScore2; 
      TestScore03=tScore3; 
      //finding avg test score 
      tAvg = ((tScore1+ tScore2 + tScore3)/300.0)*100; 
      //finding grade 
      if(tAvg>=90){ 
       tGrade="A"; 
      }else if(tAvg>=80){ 
       tGrade="B"; 
      }else if(tAvg>=70){ 
       tGrade="C"; 
      }else if(tAvg>=60){ 
       tGrade="D"; 
      }else{ 
       tGrade="F"; 
      } 
     }//end of students 
     public void listStudents(){ 
      //this function lists all of the elements of the student 
      System.out.println("\nNew Student\n Student ID: "+studentID); 
      System.out.println(" Student Name: "+ Name); 
      System.out.println(" Test 1 Score: " + TestScore01); 
      System.out.println(" Test 2 Score: " +TestScore02); 
      System.out.println(" Test 2 Score:" + TestScore03); 
      System.out.println(" Average Test Score " +tAvg); 
      System.out.println(" Grade: " + tGrade); 
     }//end of listStudents() 
     public int compareTo(Object o){ 
      //this functions compares the average test score of two students 
      if (gettAvg()<((Student)o).gettAvg()) return 1; 
      else 
       if(gettAvg()>((Student)o).gettAvg())return-1; 
        else return 0; 
     }//end of compareTo 
     public double gettAvg(){ 
      return tAvg; 
     } 
    }//end of class students 

    public static void addStudent(ArrayList<Student>AllStudents, Student workobj) 
    { 
     AllStudents.add(workobj); 
    } 

    public static void addStudent (String stdID, String sName, int tScore1,int tScore2, int tScore3){ 
     Student StudentRecord= new Student(stdID,sName,tScore1,tScore2,tScore3); 
     AllStudents.add(StudentRecord); 
    } 

    public static void deleteStudent(ArrayList<Student>studentsArrayList,String stdID) { 

     Iterator<Student> i = studentsArrayList.iterator(); 
     while (i.hasNext()) { 
      Student student = i.next(); 
      if (student.studentID.equalsIgnoreCase(stdID)) 
       i.remove(); 
     } 
    } 


    public static void sortLarge(ArrayList<Student>mylist){ 
     Student xsave, ysave; 
     int isw=1, xlast=mylist.size(); 
      while (isw==1){isw=0; 
       for (int i=0;i<=xlast-2;i++){ 
        if (((mylist.get(i)).compareTo((mylist.get(i+1)))==1)){ 
         xsave=mylist.get(i); 
         ysave=mylist.get(i+1); 
         mylist.remove(i); 
         mylist.add(i,ysave); 
         mylist.remove(i+1); 
         mylist.add(i+1,xsave); 
         isw=1; 
        } 
       }//end of for loop 
      }//end of while 
     return; 
    }//end of sortLarge 
}//end of program