difference in declaring your string array

Question

Whats the difference between this :

String [] columns = new String []{KEY_ROWID, KEY_TITLE, KEY_DESC, KEY_TIME};

And This :

String [] columns={KEY_ROWID, KEY_TITLE, KEY_DESC, KEY_TIME};

No difference. Most people prefer the second one because is sort of shorthand. — Omoro
– Omoro, Commented Mar 17, 2014 at 18:58

Keppil · Accepted Answer · 2014-03-17 18:49:54Z

1

None.

The latter version is a handy shortcut syntax that will only work in declaration statements, but the result is exactly the same.

answered Mar 17, 2014 at 18:49

Keppil

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rgettman · Accepted Answer · 2014-03-17 18:55:41Z

0

The first line uses an array creation expression that contains an array initializer, and the second line contains just the array initializer. Here, they perform the same exact function -- create and initialize an array. But only one is only valid when declaring the array.

The array initializer is defined in the JLS, Section 10.6:

An array initializer may be specified in a declaration (§8.3, §9.3, §14.4), or as part of an array creation expression (§15.10)
ArrayInitializer:
    { VariableInitializersopt ,opt }

VariableInitializers:
    VariableInitializer
    VariableInitializers , VariableInitializer

and Section 15.10 defines the array creation expression to require new SomeType[]:

An array creation expression is used to create new arrays (§10).

ArrayCreationExpression:
     new PrimitiveType DimExprs Dimsopt
     new ClassOrInterfaceType DimExprs Dimsopt
     new PrimitiveType Dims ArrayInitializer 
     new ClassOrInterfaceType Dims ArrayInitializer

DimExprs:
     DimExpr
     DimExprs DimExpr

DimExpr:
     [ Expression ]

Dims:
     [ ]
     Dims [ ]

So, you can omit the new SomeType[] part if it's part of the declaration of the array variable, but you must include it elsewhere, such as an assignment expression.

answered Mar 17, 2014 at 18:55

rgettman

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1 Comment

crushman Over a year ago

so complicating....im still a baby to this java thing. However, Thanks for going so indepth.

user2775593 · Accepted Answer · 2014-03-17 18:55:12Z

0

They produce the same instantiation (only usable in declarations) of the string array, no difference at all in the result obtained. However, I mostly choose the first one (just a personal preference).

EDIT: Sorry, I was typing while the 1st answer appeared.

answered Mar 17, 2014 at 18:55

user2775593

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