EXPRESSIONS

Parenthesized Expressions

15.7.3

15.7.2

this

The keyword

this

 may be used only in the body of an instance method or con 

structor, or in the initializer of an instance variable of a class. If it appears any 

where else, a compile time error occurs.

When used as a primary expression, the keyword

this

 denotes a value, that is

a reference to the object for which the instance method was invoked ( 15.11), or

to the object being constructed. The type of

this

 is the class

C

 within which the

keyword

this

 occurs. At run time, the class of the actual object referred to may

be the class

C

 or any subclass of

C

.

In the example:

class IntVector {

int[] v;

boolean equals(IntVector other) {

if (this == other)

return true;

if (v.length != other.v.length)

return false;

for (int i = 0; i < v.length; i++)

if (v[i] != other.v[i])

return false;

return true;

}

}

the class

IntVector

 implements a method

equals

, which compares two vectors.

If the

other

 vector is the same vector object as the one for which the

equals

method was invoked, then the check can skip the length and value comparisons.

The

equals

 method implements this check by comparing the reference to the

other

 object to

this

.

The keyword

this

 is also used in a special explicit constructor invocation

statement, which can appear at the beginning of a constructor body ( 8.6.5).

15.7.3   Parenthesized Expressions

A parenthesized expression is a primary expression whose type is the type of the

contained expression and whose value at run time is the value of the contained

expression.

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