Array of classes in java

Question

I am a beginner with java. I am trying to create the array of nested classes, and it would not work. In particularly it would not let me initialize array elements after allocation.

public class Salary {

class Person    {
    String name;
    double salary;
    void init (String n, double s)  {
        name = n;
        salary = s;
    }
}

public Salary (String args[])   {    //the input is coming in pairs: name, salary

    Person[] people;                 //creating the array
    people = new Person[10];         //allocating 10 elements in array
    int j = 0;

    for (int i = 0; i < args.length; i+=2)  {      
        people[j].init(args[i], Double.parseDouble(args[i+1]));     //trying to initialize, and that is where it's giving me an error
        System.out.format("%-15s %,10.2f%n",people[j].name, people[j].salary);
        j++;
    }
}

public static void main (String args[]) {
    new Salary(args);
 }
}

Thank you!

MadProgrammer · Accepted Answer · 2014-01-16 02:08:56Z

6

people = new Person[10]; only allocates space of 10 Person objects, it does not create them.

You need to create an instance of the object and assign to a index within the array, for example

people[j] = new Person();

Try taking a look at Arrays for ore details

You should also consider using the objects constructor rather than an init method

people[j] = new Person(args[i], Double.parseDouble(args[i+1]));

This will, of course, require you to supply a constructor.

answered Jan 16, 2014 at 2:08

MadProgrammer

348k22 gold badges243 silver badges379 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

aliteralmind Over a year ago

When MadProgrammer says "allocates space", it's like you've said, I'm going to build a house...here. And there's now a space, a lot, reserved for the house. It doesn't exist yet, though. It hasn't been built. In programming, it means there's a space for the variable, a physical location in memory, but it hasn't been created or "instantiated" yet. Nothing's been put in that space. people[j] = new Person() puts a Person object in that space.

Collectives™ on Stack Overflow

Array of classes in java

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related