Re: Life of an instance

From:
Mark Space <markspace@sbc.global.net>
Newsgroups:
comp.lang.java.help
Date:
Sun, 03 May 2009 11:56:18 -0700
Message-ID:
<qNlLl.15640$hc1.10823@flpi150.ffdc.sbc.com>
Salad wrote:

I didn't have a specific situation. I was thinking that if one had,
let's say 3 customers to process, if one reused the object cust (like in
a for loop) or if 1 held all three custs, a different instance for each
one.


Either or both work. As Lew says, using "new" and making a new object
rather than reusing one is probably less error prone. There are a few
"large" objects like the ones under Collection or a StringBuilder that
you may wish to explictly clear rather than create anew each time
through a loop. Normally, you'd only decide to do that after
performance testing revealed that calling "new" was a bottleneck.

To process three customers, use an array or Collection:

   public Customer[] test2() {
     Customer[] custArray = new Customer[3];
     for( int i = 0; i < custArray.length; i++ ) {
       custArray[i] = new Customer();
       // more processing here...
     }
     return custArray;
   }

All three Customer objects remain in scope here because the custArray
object retains references to them. Eric Sosman was explaining this in
his post.

For a Collection of some sort:

   public List<Customer> test2() {
     ArrayList<Customer> custs = new ArrayList<Customer>();
     for( int i = 0; i < 3; i++ ) {
       Customer c = new Customer();
       custs.add( c );
       // more processing here...
     }
     return custs;
   }

Again, these three Customer objects are preserved because the ArrayList
holds a reference to them.

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