Passing array as a parameter of object problem

Question

I want to pass array as a parameter of object but I am kind of stack. So here is my problem.

public class Publisher {

    public static void main(String args[]) {
        String teachers[] = {"Jyothi", "Jyostna", "Sumathi"};
        Publisher2 p1 = new Publisher2(teachers[1],20);       //The problem is here, I can't specify 
     //index of array (I can put onlu teachers without index[1])so toString method is returning address of object instead of the name
        System.out.println(p1);
    }
}

class Publisher2 {

    String[] teachers;
    int y;

    public Publisher2(String[] teachers, int y) {
        this.teachers = teachers;
        this.y = y;
    }

    @Override
    public String toString() {
        return "Publisher2{" + "teachers=" + teachers + ", y=" + y + '}';
    }
}

Elliott Frisch · Accepted Answer · 2019-12-23 21:18:22Z

2

teachers[1] is the second element in your array. The array itself is just teachers. Like,

Publisher2 p1 = new Publisher2(teachers, 20);

answered Dec 23, 2019 at 21:18

Elliott Frisch

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6 Comments

Ivan Pantic Over a year ago

That's it...But I want p1 object to consist that second element and not the hole array. For example I want toString method to write : Publisher2{teachers=Jyostna, y=20} and for p2 :Publisher2{teachers=Sumathi, y=20}...

Elliott Frisch Over a year ago

Then it should take one String, not an array of String(s).

Ivan Pantic Over a year ago

I was hopping for some better solution... :)

Elliott Frisch Over a year ago

Teachers is plural... you might want to clarify how/why one teacher is now multiple.

Ivan Pantic Over a year ago

Well... For example i have one array (doesn't have to be called teacher and it may be String as well as int ) and I have objects o1,o2,o3 with two parameters. One of that parameters for o1 has to be index[1] of that array, for other object o2 parameter has to be index[2], and for o3 parameter has to be index[2]. So, I can not find solution for that...Should I write some method or something?

|

hjoeren · Accepted Answer · 2019-12-23 22:11:47Z

0

Another possibility would be to use varargs and swap the parameters (the varargs have to be the last in the parameter list):

public Publisher2(int y, String... teachers) {
  this.teachers = teachers;                   
  this.y = y;                                 
}

With this approach you can pass as many arguments (none, a single, multiple or an array):

new Publisher2(20);
new Publisher2(20, teachers[0]);
new Publisher2(20, teachers);

With the toString problem you can use java.util.Arrays, so that the toString looks like this:

@Override                                                                           
public String toString() {                                                          
  return "Publisher2{" + "teachers=" + Arrays.toString(teachers) + ", y=" + y + "}";
}

The strings then will look like

Publisher2{teachers=[], y=20} // for new Publisher(20)
Publisher2{teachers=[Jyostna], y=20} // for new Publisher(20, teachers[1])
Publisher2{teachers=[Jyothi, Jyostna, Sumathi], y=20}
 // for new Publisher(20, teachers)

answered Dec 23, 2019 at 22:11

hjoeren

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4 Comments

Ivan Pantic Over a year ago

Thank you very much. Varargs are also very good approach. Both answers are great.

AndrewF Over a year ago

varargs might help for syntactic convenience but does not help with the problem as presented.

hjoeren Over a year ago

@AndrewF Why doesn't this help to the problem as presented? With the varargs the step to manually create an array gets passed to the compiler, so new Publisher2(20, teachers[1]) gets compiled to new Publisher2(20, new String[]{teachers[1]})

AndrewF Over a year ago

The problem statement: "I want to pass array as a parameter of object" -- that is, there is one specific set/type data that the author wants to pass. Implementing with varargs would allow for multiple arity with the same call syntax (and also for quietly converting discrete parameters into an array), which might be convenient for other use cases, but if the caller knows what they want to pass, then the method should be typed specifically to allow that one input.

AndrewF · Accepted Answer · 2019-12-25 00:50:16Z

0

Since you have clarified your question in various comments (please edit your question), we now know that you want to pass a single item, but you have implied in code and comments that Publisher2 must be constructed with an array as a parameter.

Therefore, you will need to build a new array containing the single item.

String[] teacherSubset = new String[] { teachers[1] };
Publisher2 p1 = new Publisher2(teacherSubset, 20);

or...

Publisher2 p1 = new Publisher2(new String[] { teachers[1] }, 20);

Please edit your question so that it is clear about exactly what you are trying to accomplish.

answered Dec 25, 2019 at 0:50

AndrewF

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