一遍又一遍地阵列打印相同的单元格

Question

I'm having a user enter data First Name, Last Name, and Number. The problem is when I print out the array, it will only print out the last entered data.

For example if a user enters: (F,V 12345) (L,K 2345) (R,G 4555) //Initials used instead of names

The program would print out:

R,G 4555 R,G 4555 R,G 4555

Datab.java

 public Datab()
{
    first = null;
    last = null;
    cell = null;
}

public Datab(String f, String l, String c)
{
    first=f;
    last=l;
    cell=c;

}
public static String getFirst(Datab friends)
{
    Scanner kb = new Scanner(System.in);
    System.out.println("Enter First name: ");
    first = kb.next();
    return first;

}
public static String getLast(Datab friends)
{
    Scanner kb = new Scanner(System.in);
    System.out.println("Enter Last name: ");
    last = kb.next();


    return last;  
} 
public static String getCell(Datab friends)
{
    Scanner kb = new Scanner(System.in);
    System.out.println("Enter Cell Number: ");
    cell = kb.next();

    return cell;

}



 public String toString(){




 return (first + " ,"+" "+ last + " "+ cell);



   }

}

DBMS.java

Datab[] friends = new Datab[n];


    for (int i = 0; i < friends.length; i++) {
        friends[i] = new Datab();
        System.out.println("\nFilling object #: " + (i + 1));



        friends[i].getFirst(friends[i]);

        friends[i].getLast(friends[i]);
        friends[i].getCell(friends[i]);


    }

for(int x=0; x<friends.length; x++){

            System.out.println(friends[x]);
        }

Answer 1

Reason you have defined your variable first, last, cell as static.

You should remove static and make it is instance specific. Same applies for method as well.

When you make a variable as static, you just have one instance of the same and whatever you assigned value at last, is the one you are going to see and hence you see the same value being printed irrespective of what you assigned before.

Answer 2

Variables first , last , cell are static. Also, the methods getFirst() , getLast() , getCell() defined for initializing the variables are static.

There is only one single copy created for static members(variables and members) for all the instances of a class. So, in your case, all the instances of class Datab, ie, friends[] refers to same copy of variables first, last, cell.

Removing static keyword from variable declaration and methods will solve the problem, as all the instances of Datab will point to different variables.