java - My ArrayList only contains the last item on my array -

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• why arraylist contain n copies of last item added list? 3 answers

public static void main(string args[]){               new converter();  //the converter()  method reads csv file pass array of string // called stringlist;  in stringlist  static variable;      arraylist<student> list = new arraylist<student>(5);     string p[] = null;     student stud = null;     for(int z = 0; z < stringlist.length; z++){         p = stringlist[z].split(",");          id = integer.parseint(p[0]);          yr = integer.parseint(p[5]);          fname = p[1];          gname = p[2];          mname = p[3].charat(0);          course = p[4];          stud = new student(id,yr,fname,gname,mname,course);         studs = stud; 

i tried display current values of variables above , compare them student object

    system.out.println(id +" "+ yr +" "+ fname + " "+gname + " "+mname + " "+course +"  should same : " +stud.tostring());         list.add(studs);    // add student object list      }  //end of loop 

then noticed arraylist displays 1 value:

    (int c = 0; c<list.size(); c++){         system.out.println(" @list "+c+": "+list.get(c));     } } // end of main method 

normally read 100+ items example made 5; out put of program;

      2123259 1 avila jeremy raymund t bsit should same :    2123259,avila,jeremy raymund,t,bsit,1       2124919 1 beroÑa maynard w bsit should same : 2124919,beroÑa,maynard,w,bsit,1       2124679 1 cabrera jerson rhod d bsit should same :      2124679,cabrera,jerson rhod,d,bsit,1       2124905 1 cabrillas armando jr. b bsit should same : 2124905,cabrillas,armando jr.,b,bsit,1       2123400 1 cariÑo jvanz s bsit should same : 2123400,cariÑo,jvanz,s,bsit,1        @list 0: 2123400,cariÑo,jvanz,s,bsit,1       @list 1: 2123400,cariÑo,jvanz,s,bsit,1       @list 2: 2123400,cariÑo,jvanz,s,bsit,1       @list 3: 2123400,cariÑo,jvanz,s,bsit,1       @list 4: 2123400,cariÑo,jvanz,s,bsit,1 

now problem here ladies , gentlemen tried display stud object inorder check if reading correct values , indeed displays correctly, , after assigning values , add list. confuses me , , couldnt figure out why list contains last item in array? please me, i've been stuck 2 nights.

this whole code , focus on main

public class converter {

    private static arraylist<student> students;     private static string[] stringlist;     private static scanner fr;     private static int size;     private static int id;     private static int yr;     private static string fname;     private static string gname;     private static char mname;     private static string course;   public static void main(string args[]){     arraylist<student> list = new arraylist<student>(5);     new converter();     string p[] = null;     student stud = null;       students = new arraylist<student>(stringlist.length);     for(int z = 0; z < stringlist.length; z++){         p = stringlist[z].split(",");         id = integer.parseint(p[0]);         yr = integer.parseint(p[5]);         fname = p[1];         gname = p[2];         mname = p[3].charat(0);         course = p[4];         stud = new student(id,yr,fname,gname,mname,course);          system.out.println(id +" "+ yr +" "+ fname + " "+gname + " "+mname + " "+course +" should same : " +stud.tostring());         list.add(stud);      }  // end of loop     (int c = 0; c<list.size(); c++){         system.out.println(" @list "+c+": "+list.get(c));     } // end of second loop }// end of main public converter(){      readstudtentscsv();     id = 0;     yr = 0;     fname = "";     gname = "";     mname = ' ';     course = ""; }  public static void readstudtentscsv() {         int s = 0;         try {             size = countlines("test.csv");             stringlist = new string[size];             fr = new scanner(new file("test.csv"));           } catch(exception e){             e.printstacktrace();         }          while (fr.hasnextline()){             stringlist[s] = fr.nextline();             //system.out.println(stringlist[s]);             s++;          }     }  public static int countlines(string efile) throws exception{          scanner fscan = new scanner(new file(efile));         int count =0;         while (fscan.hasnextline()){         count += 1;         string line = fscan.nextline();         }         fscan.close();         return count;     } 

}

the problem fields in student class static. haven't shown code, guessed this:

public class student {      private static int id;     //other fields...     //constructor...     //getters , setters... } 

just remove static marker fields in class.

public class student {      //field must not static     private int id;      //other non-static fields...     //constructor...     //getters , setters... } 

note removing static marker in fields of converter class won't fix problem.

in short, static fields belong class, while non-static fields belong class object reference. if having static fields in student class, object references share value. when having non-static fields, since belong each instance of class, every object reference will have different value.

more info: understanding instance , class members