Java: efficient way of memory allocation for an array of objects

Question

In the code below I am trying to avoid the last three lines which allocate memory for the instances of class. Any suggestions on how to bring the memory allocation part inside the class definition? So what I want to do is to be able to execute pInfo[0].sValue="string"; right after AClass [] pInfo = new AClass[10];

  class AClass {
     private String sName="";
     private String sValue="";
  }

    AClass [] pInfo = new AClass[10];

   // how to avoid the code below or bring them into class definition?  

    pInfo[0] = new AClass();
    pInfo[1] = new AClass();
      ... 
    pInfo[9] = new AClass();

EDIT: what I mean by efficiency is in the amount of code + code readability

It might be nicer to take advantage of constructor arguments to initialize the fields, so you can write it like: AClass[] pInfo = new AClass[] { new AClass("name-1", "value-1"), ... }; — obataku
– obataku, Commented Jul 31, 2012 at 20:24

Woot4Moo · Accepted Answer · 2012-07-31 20:17:50Z

7

AClass[] pInfo = {new AClass(),new AClass(), etc.};

OR

AClass[] pInfo = new AClass[10];

for(int i = 0; i < pInfo.length; i++)  
{  
    pInfo[i] = new AClass();  
}

answered Jul 31, 2012 at 20:17

Woot4Moo

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Comments

Jeffrey · Accepted Answer · 2012-07-31 20:20:41Z

1

There is no way to avoid that, you will need to explicitly assign a value to each element of your array.

JLS §10.3 states that arrays provide initial values for their elements when they are created.

JLS §4.12.5 states that the initial value for reference types is null.

answered Jul 31, 2012 at 20:20

Jeffrey

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Comments

Chris Dargis · Accepted Answer · 2012-07-31 20:28:34Z

1

You can try something like this:

class AClass {
     public String sName="";
     public String sValue="";
}

class AClassArray {
     public AClass[] pInfo;

     public AClassArray() {
        pInfo = new AClass[10];
        for(int i = 0; i < pInfo.length; i++)  
           pInfo[i] = new AClass();  
     }
}

Use:

AClassArray aClassArray = new AclassArray();
aClassArray.pInfo[i].sXXXX;

edited Jul 31, 2012 at 20:28

answered Jul 31, 2012 at 20:19

Chris Dargis

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6 Comments

Chris Dargis Over a year ago

@Woot4Moo: Hit submit too soon

Code-Apprentice Over a year ago

This works, but isn't very extensible. You might as well use a Vector or List rather than reinventing the wheel.

Chris Dargis Over a year ago

@Code-Guru: Of course not! The underlying data structure is an array!

Code-Apprentice Over a year ago

@DougRamsey What if I want to create BClass and have an array of this new class? Now I will have to write a BClassArray. On the other hand, a generic collection such as Vector or List will work with any class I choose without writing a customized Array class for it. (Perhaps "extensible" isn't quite the right word to describe this issue...)

Code-Apprentice Over a year ago

@DougRamsey That may be...I'm not up on all the language changes since Java 5 ;-(

|

Nitin Chhajer · Accepted Answer · 2012-07-31 20:38:01Z

0

class AClass {
   private String sName="";
   private String sValue="";

   public static final AClass[] getArrayOfObjs(int size){
    if(size <= 0)
       return null; //You can also create your custom exception to be thrown here
    AClass[] array = new AClass[size];

    for(int i = 0; i < size; i++)  
    {  
       array[i] = new AClass();  
    }  
    return array;
  }
}

Then instantiate as

AClass [] pInfo = AClass.getArrayOfObjs(10);

edited Jul 31, 2012 at 20:38

answered Jul 31, 2012 at 20:23

Nitin Chhajer

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1 Comment

Woot4Moo Over a year ago

if size < 0, this object can be exploited because it will throw an exception and is not final.

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