How to create an array of objects

Question

I thought this was pretty simple, because I am pretty sure I have done it before, but I cant seem to get this to work. My class is:

public class City
{
    String start = null;
    String end = null;
    int weight = 0;
}

and I am doing:

City cityGraph[] = new City[l];

When I try to access cityGraph[x].start for example, I get a null pointer exception, so I figured I need to initialize every element in the array as well, so I do:

for(int j = 0; j < l; j++)
        {
            cityGraph[j] = new City();
        }

but it is giving me this error:

No enclosing instance of type Graphs is accessible. 
Must qualify the allocation with an enclosing instance 
of type Graphs (e.g. x.new A() where x is an instance of Graphs).

I have no idea what this means, or how to fix it. Any help would be appreciated!

It seems to think you are trying to use type Graphs. Could you post the entire code as is and see if there's a typo? — nolegs, Jul 18 '12 at 14:39
Possible duplicate of [Java - No enclosing instance of type Foo is accessible](http://stackoverflow.com/questions/9560600/java-no-enclosing-instance-of-type-foo-is-accessible) — fabian, Mar 04 '16 at 00:36

score 5 · Accepted Answer · edited Jun 20 '20 at 09:12

That can happen when you have declared public class City as an inner class of public class Graphs like so

public class Graphs {

    public class City {
    
    }

}

This way the City cannot be constructed without constructing a Graphs instance first.

You'd need to construct the City as follows:

cityGraph[j] = new Graphs().new City();
// or
cityGraph[j] = existingGraphsInstance.new City();

This makes honestly no sense. Rather either extract the City into a standalone class,

public class Graphs {

}

public class City {

}

or make it a static nested class by declaring it static.

public class Graphs {

    public static class City {
    
    }

}

Either way, you'll be able to construct a new City by just new City().

How to create an array of objects

3 Answers3

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