CLASSES

Initialization of Fields

8.3.2

If the declarator is for a class variable (that is, a

static

 field), then the vari 

able initializer is evaluated and the assignment performed exactly once, when

the class is initialized ( 12.4).

If the declarator is for an instance variable (that is, a field that is not

static

),

then the variable initializer is evaluated and the assignment performed each

time an instance of the class is created ( 12.5).

The example:

class Point {

int x = 1, y = 5;

}

class Test {

public static void main(String[] args) {

Point p = new Point();

System.out.println(p.x + ", " + p.y);

}

}

produces the output:

1, 5

because the assignments to

x

 and

y

 occur whenever a new

Point

 is created.

Variable initializers are also used in local variable declaration statements

( 14.3), where the initializer is evaluated and the assignment performed each time

the local variable declaration statement is executed.

It is a compile time error if the evaluation of a variable initializer for a field of

a class (or interface) can complete abruptly with a checked exception ( 11.2).

8.3.2.1

Initializers for Class Variables

A compile time error occurs if an initialization expression for a class variable con 

tains a use by a simple name of that class variable or of another class variable

whose declaration occurs to its right (that is, textually later) in the same class.

Thus:

class Test {

static float f = j;

//

compile time error: forward reference

static int j = 1;

static int k = k+1;

//

compile time error: forward reference

}

causes two compile time errors, because

j

 is referred to in the initialization of

f

before

j

 is declared and because the initialization of

k

 refers to

k

 itself.

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