Getting Null pointer while setting array of objects

[Deepak harsha]

Hi All, I am getting Null Pointer error while trying to set an array of objects for the following getter setter class.
I am relatively new to Java, can someone help me to find out the right way to do this.

Thanks,
Deepak

package org.lab.test;

public class ExecParameters {


	private String url;
	private String username;
	private String password;
	public String getUrl() {
		return url;
	}
	public void setUrl(String url) {
		this.url = url;
	}
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
	
}

package org.lab.test;

public class testParameters {
	
	private static ExecParameters[] setExec(){
		ExecParameters[] execParameters = new ExecParameters[3];
		for(int i =0; i< 3; i++){
		
		execParameters[i].setUrl(i+"aURL");
		execParameters[i].setUsername(i+"ausername");
		execParameters[i].setPassword(i+"apassword");
		}
		return execParameters;
	}
	public static void main(String args[]){
		ExecParameters[] execParameters = setExec();
		for(int i =0; i< execParameters.length; i++){
			System.out.println("---------------X"+i+"X--------------------");
			
			System.out.println(execParameters[i].getUrl());   //Getting Null pointer here
			System.out.println(execParameters[i].getUsername()); //Getting Null pointer here
			System.out.println(execParameters[i].getPassword()); //Getting Null pointer here
		}
	}

}

[Michal Czubek]

line 8 in testParameters is missing

execParameters[i] = new ExecParameters();

Here: ExecParameters[] execParameters = new ExecParameters[3]; you're only allocating memory for array and array of ExecParameters is filled with null objects. I don't know how you get into line 20 ;)

[Prasad prap]

Remember null pointer exceptions are always due to no object creation.

[fred rosenberger]

If you are getting an error, please post it, in its entirety here. Those error messages tell you EXACTLY where the problem is. Your job when posting here is to make it as easy as possible for us to help you, and posting that message is a basic requirement.

[Stevens Miller]

Prasad prap wrote:Remember null pointer exceptions are always due to no object creation.

"Always" is a little strong, Prasad. null can be assigned as well:

package nulltest;

import java.io.File;

public class NullTest
{
    public static void main(String[] args)
    {
        File f = new File("filename.dat");
        
        System.out.println(f.getName());
        
        f = null;
        
        System.out.println(f.getName());
    }
}

Output:

filename.dat
Exception in thread "main" java.lang.NullPointerException
	at nulltest.NullTest.main(NullTest.java:13)

And, one should not be confused into thinking that "null" is somehow an illegal value for an object variable to have in it, or even pass to another object's methods. For example:

package nulltest;

import java.io.File;

public class NullTest
{
    public static void main(String[] args)
    {
        File f = new File("filename.dat");
        
        System.out.println(f);
        
        f = null;
        
        System.out.println(f);
    }
}

Gets you this:

filename.dat
null

You know, I would love to get my hands on the person who decided to name that one NullPointerException. C/C++ programmers who learn Java all have to come to terms with the words, "there are no pointers in Java." (Well, I had to, anyway.) Object variables with null in them are part of what a Java programmer has to understand. Tossing error messages with the word "pointer" embedded in them at a new Java coder just adds to the confusion.