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initialize an array of booleans

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  initialize an array of booleans "bob smith" <bob.smith@1:261/38.remove-s5i-this> - 2012-08-01 18:09 +0000
    Re: initialize an array of booleans "Eric Sosman" <eric.sosman@1:261/38.remove-s5i-this> - 2012-08-01 18:09 +0000
    Re: initialize an array of booleans "Lew" <lew@1:261/38.remove-s5i-this> - 2012-08-01 18:09 +0000
    Re: initialize an array of booleans "Roedy Green" <roedy.green@1:261/38.remove-s5i-this> - 2012-08-01 18:09 +0000

#16908 — initialize an array of booleans

From: bob smith <bob@coolfone.comze.com>

Is there any easy way to initialize an array of booleans like this?

boolean b[] = new boolean(false)[100];

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#16924

  To: bob smith
From: Eric Sosman <esosman@ieee-dot-org.invalid>

On 7/31/2012 3:58 PM, bob smith wrote:
> Is there any easy way to initialize an array of booleans like this?
>
> boolean b[] = new boolean(false)[100];

     Sure: `boolean b[] = new boolean[100];' will do it, although
`boolean[] b = new boolean[100];' is usually considered better style.

     ... but that's just because a freshly-created boolean is `false'
until and unless it's given another value, just as a freshly-created int is 
zero.  To initialize with a lot of `true's you could write

        boolean[] b = new boolean[]{true,true,true, /*etc.*/};

... but that would be tedious, error-prone, and inefficient (you'd be dismayed 
at the number of byte code instructions generated). It'd be better to use a 
loop, either in open code:

        boolean[] b = new boolean[100];
        for (int i = 0; i < b.length; ++i)
            b[i] = true;

... or with the prepackaged array-filling method:

        boolean[] b = new boolean[100];
        java.util.Arrays.fill(b, true);

--
Eric Sosman
esosman@ieee-dot-org.invalid

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#16925

  To: bob smith
From: Lew <lewbloch@gmail.com>

On Tuesday, July 31, 2012 12:58:58 PM UTC-7, bob smith wrote:
> Is there any easy way to initialize an array of booleans like this?
>
>
>
> boolean b[] = new boolean(false)[100];

boolean b[] = new boolean [100];

<http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.10.1>

If you want to initialize array elements to a value that is not the default you 
have to loop.

Or use the 'java.util.Arrays' class.
<http://docs.oracle.com/javase/7/docs/api/java/util/Arrays.html#fill(boolean[],
boolean)>

Every Java programmer should know the collections framework and key utility 
classes like 'Arrays'.

--
Lew

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#16926

  To: bob smith
From: Roedy Green <see_website@mindprod.com.invalid>

On Tue, 31 Jul 2012 12:58:58 -0700 (PDT), bob smith
<bob@coolfone.comze.com> wrote, quoted or indirectly quoted someone
who said :

>Is there any easy way to initialize an array of booleans like this?
>
>boolean b[] = new boolean(false)[100];

for basic info on arrays including initialisation, see 
http://mindprod.com/jgloss/array.html

For this kind of info, a basic text book, even an out-of-date free one is 
invaluable.
--
Roedy Green Canadian Mind Products
http://mindprod.com
The greatest shortcoming of the human race is our inability to understand the 
exponential function.
 ~ Dr. Albert A. Bartlett (born: 1923-03-21 age: 89)
http://www.youtube.com/watch?v=F-QA2rkpBSY

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