8.6

Constructor Declarations

CLASSES

class Test {

public static void main(String[] args) {

System.out.println(Z.i);

}

}

produces the output:

0

because the variable initializer for

i

 uses the class method

peek

 to access the

value of the variable

j

 before

j

 has been initialized by its variable initializer, at

which point it still has its default value ( 4.5.4).

If a

return

 statement ( 14.15) appears anywhere within a static initializer,

then a compile time error occurs.

If the keyword

this

 ( 15.7.2) or the keyword

super

 ( 15.10,  15.11) appears

anywhere within a static initializer, then a compile time error occurs.

8.6   Constructor Declarations

The constructor of wharves, bridges, piers, bulk heads,

floats, stays against the sea . . .

 Walt Whitman,

Song of the Broad Axe

 (1856)

A

constructor

 is used in the creation of an object that is an instance of a class:

ConstructorDeclaration:

ConstructorModifiers

opt

ConstructorDeclarator

Throws

opt

ConstructorBody

ConstructorDeclarator:

SimpleTypeName

 (

FormalParameterList

opt

 )

The

SimpleTypeName

in the

ConstructorDeclarator

 must be the simple name of

the class that contains the constructor declaration; otherwise a compile time error

occurs. In all other respects, the constructor declaration looks just like a method

declaration that has no result type.

Here is a simple example:

class Point {

int x, y;

Point(int x, int y) { this.x = x; this.y = y; }

}

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