Creating an array of objects with constructor in Java

Question

If I have the following class:

public class Hello {
  private String name;

  public Hello(String n) {
    this.name = n;
  }

  public int getSize(int x) {
   return x + (this.name.length());      
  }
}

Now if I wish to create an array of 5 Hello objects, I could say

Hello[] t = new Hello[5];

My question is:

i) How do I call the constructor on each of elements of the array t

ii) After I have called the constructor, how can I call the method and pass the argument x to each element of the array?

Luiggi Mendoza · Accepted Answer · 2014-10-30 22:53:58Z

3

i) How do I call the constructor on each of elements of the array t

Traverse each element of the array and initialize the elements using the proper constructor and arguments:

for (int i = 0; i < t.length; i++) {
    t[i] = new Hello("some string");
}

ii) After I have called the constructor, how can I call the method and pass the argument x to each element of the array?

Again, traverse the array and call the desired method on the array element.

int x = ...; //define some value
for (int i = 0; i < t.length; i++) {
    System.out.println(t[i].getSize(x));
}

answered Oct 30, 2014 at 22:53

Luiggi Mendoza

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4 Comments

MiltoxBeyond Over a year ago

also can be: Hello[] t = { new Hello("blah"), new Hello("blah") }; Just to be more complete...

Luiggi Mendoza Over a year ago

@MiltoxBeyond that's just another way to initialize an array. But this answer tries to use OP's code.

MiltoxBeyond Over a year ago

I didn't say complete, just more complete so he knows there are different ways to do it.

Luiggi Mendoza Over a year ago

@MiltoxBeyond sorry, I was stopped while writing that comment. And yes, that's another option to initialize the array, but I'm not using it since OP seems to be in learning phase.

mattforni · Accepted Answer · 2014-10-30 23:13:22Z

If you want each instance of Hello to contain a different string I'd initialize an array of strings first and then iterate over those to create the array of Hello instances. You also don't need to traverse the array twice, as you can initialize and then call the method. You could also abstract this into a static method in the Hello class as a static constructor.

public class Hello {
    ...
    public static final Hello[] fromStrings(final String[] words, final int x) {
        final Hello[] hellos = new Hello[words.length];
        for (int i = 0; i < words.length; i++) {
            hellos[i] = new Hello(words[i]);
            System.out.println(hellos[i].getSize(x));
        }
        return hellos;
    }
}

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