Create Java Object On-Demand

Question

I have a java private method and I am trying to find the best way to create an object inside the method. Following are two different approaches that I am trying:

Approach A:

 private void createObject() {
     Object A;
     if (conditionA) {
         A = new Object();
         //do some Action X with object A
     } else {
         //Do something without object A
         if (conditionB) {
             return;
         }
         A = new Object();
         //do some Action Y with object A
     }
     return;
 }

Approach B:

 private void createObject() {
     Object A = new Object()
     if (conditionA) {
         //do some action X with Object A
     } else {
         //Do something without Object A
         if (conditionB) {
             return;
         }
         //do some action Y with Object A
     }
     return;
 }

Obviously both the code snippets are working and without any issues. I am just trying to find out the better coding style and standard.

Tell us more about your intended use-case and the problem you're trying to solve instead. Perhaps you've overly complicated the matter. — Janez Kuhar
– Janez Kuhar, Commented Jan 24, 2019 at 8:58

Bentaye · Accepted Answer · 2019-01-24 10:09:32Z

1

Let's write the truth table

  A  |   B   |      Expected Outcome               
-----+-------+-------------------------------
True | True  | do X with object A               
True | False | do X with object A               
False| False | do Y with object A               
False| True  | do something without object A 
-----+-------+-------------------------------

I think this translates to:

boolean doXWithA = conditionA;
boolean doYWithA = !conditionA && !conditionB;
boolean doSomethingWithA = doXWithA || doYWithA;
if(doSomethingWithA)
    Object a = new Object();
    if (doXWithA) {
        // do X with object A 
    } else if (doXWithB) {
        // do X with object B 
    }
} else {
    // do something without object A 
}

Good practice is to reduce the scope of variables as much as possible. And if the instantiation is expensive, you also want to reduce the number of time you instantiate it. Here Object a is only initialised when necessary and its scope is as small as possible (only one if block)

edited Jan 24, 2019 at 10:09

answered Jan 24, 2019 at 9:32

Bentaye

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1 Comment

Sandeep Over a year ago

The do something are two different things. Edited above. My bad

puffy.bun · Accepted Answer · 2019-01-24 08:53:23Z

0

I believe that if you want to initialize object with default value you should do this in the place of declaration

Object A = new Object();
if (conditionA) {
    ...
}

answered Jan 24, 2019 at 8:53

puffy.bun

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Comments

Ninad Pingale · Accepted Answer · 2019-01-24 08:59:32Z

0

Approach A is better.

In that, Consider "if" condition is not satisfied and it goes in "else".

There if conditionB is satisfied, then it will return.So memory is not allocated to A.

In Approach B, unnecessarily memory allocation is done which is of no use in above scenario.

answered Jan 24, 2019 at 8:59

Ninad Pingale

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Comments

glglgl · Accepted Answer · 2019-01-24 09:12:23Z

0

I would go with approach A, as it is only necessary to initialize the object when needed.

If the initialization of that object is rather complicated, in order to avoid repeating yourself, you either define a static helper method in order to initialize the object or you go via a Supplier<>:

Supplier<Type> objSupplier = () -> new Type(a, b, c, d, whatever)

and then, at the two places where the object is supposed to be created, you do

A = objSupplier.get();

(note that variables are usually written in lowercase/camelCase).

answered Jan 24, 2019 at 9:12

glglgl

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1 Comment

Luke Garrigan Over a year ago

I think this is way out of scope of the question, OP specifically defines his problems and possible solutions.

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