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initialize an array of booleans

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  initialize an array of booleans bob smith <bob@coolfone.comze.com> - 2012-07-31 12:58 -0700
    Re: initialize an array of booleans Lew <lewbloch@gmail.com> - 2012-07-31 13:08 -0700
    Re: initialize an array of booleans Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-07-31 16:12 -0400
    Re: initialize an array of booleans Roedy Green <see_website@mindprod.com.invalid> - 2012-07-31 14:08 -0700

#16800 — initialize an array of booleans

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

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

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#16893

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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#16894

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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#16895

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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