, , . , . , , . , , . .
, . , . , - , . , . .
Java : , , . Java C++, . C++ , . , , , .
, , . , , . .
null, , . . Java null, . , . (Run-time error). Java () null :
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException.
, . , , , .
|
|
, -. , . null ( , ==0), , null. , Java ==, =, .
, ( ), ( ). , , , . , , , .
new, , , , , . , .
. , circle1 Circle ( null). null.
circle1 Circle
null
circle1=new Circle(x1,y1,r1);
- x1, y1 r1 ( - , ):
1 Circle
circle1
, . , circle1 1, circle1 , . , , circle1.
, , . circle2 Circle,
circle2= circle1;
, .
:
Circle circle1=new Circle(x1,y1,r1);
Circle circle2=new Circle(x2,y2,r2);
Circle circle3;
:
1 Circle
circle1
|
2 Circle
circle2
|
circle3
|
null
circle3=circle2;
:
|
|
1 Circle
circle1
|
2 Circle
circle2
|
circle3
|
, circle2, circle3, 2. 2. , , , . , circle2.x x2, , circle3.x. , circle2.x, circle3.x x 2.
,
circle1=circle2;
, circle1 .
1 Circle
|
circle1
|
2 Circle
circle2
|
circle3
|
2 , , : circle1, circle2 circle3. 1 , , . , .
, . Java , . (garbage collection) . Java-, . Java, C/C++ Object PASCAL, , .
, , . , , . , , , . , , , .