Returning array in Java

When I run this code,

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */


class Posting
{
    String title;
}

public class Test
{
    Posting[] dew()
    {
        Posting[] p = new Posting[100];
        for(int i = 0; i <p.length; i++)
        {
            p[i].title  = "this is " + i;
        }
        return p;
    }

    public static void main(String args[])
    {
    开发者_运维知识库    Test t = new Test();
        Posting[] out = t.dew();

        for(int i = 0; i < out.length; i ++)
        {
            System.out.println(out[i].title);
        }
    }
}

I get this error, run:

Exception in thread "main" java.lang.NullPointerException
    at mistAcademic.javaProject.newsBot.core.Test.dew(Test.java:20)
    at mistAcademic.javaProject.newsBot.core.Test.main(Test.java:29)
Java Result: 1
BUILD SUCCESSFUL (total time: 1 second)

Could you have any idea?

---

You have to initialize the array element before setting fields on it.

p[i] = new Posting(/* ... */);
// THEN set the fields
p[i].title = /* ... */;

---

Posting[] p = new Posting[100];

This will only create the array itself, all entries are set to null.

So you need to create the instances and put them into the array as well.

    for( int i = 0; i <p.length ; i++ )
    {
        p[i] = new Posting();    // <=  create instances
        p[i].title  = "this is " + i ;
    }

---

you have to init your postings

Posting[] dew()
    {
        Posting[] p = new Posting[100];

        for( int i = 0; i <p.length ; i++ )
        {
            p[i] = new Posting();
            p[i].title  = "this is " + i ;
        }

        return p ;
    }

---

You need to initialize each object of the array. Add following lines before

p[i] = new Posting();
p[i].title  = "this is " + i ; in the for loop.

---

By doing : Posting[] p = new Posting[100];

will create an array of 100 null objects. p[0], p[1], p[2]..... p[99] = null so when you do :

 p[i].title 

its actually same as : null.title and hence you get NullPOinterException.