1. Primitive Values Vs Objects Wrapper Classes Memory Representation of Primitive Values Vs Objects –Pointers Equal Vs == Sharing of Objects Garbage Collection

2. vector.elementAt(3) 5new Integer(5) Wrapper Classes AStringDatabase AStringHistoryString Object intbooleanchardouble wrapper class “Joe Doe”.toString() 5.toString() Vector vector = new Vector() vector.addElement(“Joe Doe”) vector.addElement(5) vector.addElement(new Integer(5)) (new Integer(5)).toString() vector.elementAt(3).intValue() Number Integer Double wrapper class

3. Other Wrapper Classes Double –public Double(double value) –public double doubleValue() Boolean –public Boolean(boolean value) –public boolean booleanValue() Character –public Character(char value) –public char charValue() Float, Short, Long

4. Storing Primitive Values/Variables 5 5.5 48 double d 52 int i 80 double e 85.5 5 16 5 int i = 5; memory address double d = 5.5; same size same, double size double e = d;

5. Storing Objects Values/Variables 16 8 5.5 Double@8 860 Integer I 5 16 Integer@16 48 Double D Integer I = new Integer(5) Double D = new Double(5.5) memory address different sizes variables same size

6. Structured Objects public class APoint implements Point { int x, y; public APoint (int initX, int initY) { x = initX; y = initY; } public int getX() {return x}; public void setX(int newVal) {x = newVal;} public int getY() {return y}; public void setY(int newVal) {y = newVal;} }

7. Structured Objects 16 80 5.5 Double@8 860 Integer I 5 16 Integer@16 96 Point p 50 100 80 APoint@80 48 Double D public class APoint implements Point { // instance vars int x, y; //methods … } Point p = new APoint(50, 100)

8. Inheritance public class ABoundedPoint extends APoint { APoint upperLeftCorner, lowerRightCorner; public ABoundedPoint (int initX, int initY, Point initUpperLeftCorner, Point initLowerRightCorner) { super(initX, initY); upperLeftCorner = initUpperLeftCorner; lowerRightCorner = initLowerRightCorner; } … } Superclass Constructor

9. Inheritance public class APoint implements Point { int x, y; … } new ABoundedPoint(75, 75, new APoint(50,50), new APoint(100,100) ) 8 16 50 APoint@8 8 48 ABounded Point@48 100 16 APoint@16 100 75 public class ABoundedPoint extends APoint { Point upperLeftCorner ; Point lowerRightCorner; … }

10. Assignment of Object Variables Point p1 = new APoint(50, 50); Point p2 = p1; 50 APoint@8 8 8 16 Point p1 8 48 Point p2 P1P2 APoint@8 p1.setX(100);

11. Assignment of Object Variables Point p1 = new APoint(50, 50); Point p2 = p1; 100 50 APoint@8 8 16 8 Point p1 8 48 Point p2 p1.setX(100); p2.getX()  100 P1P2 APoint@8 p1 = new APoint(200,200);

12. Assignment of Object Variables 100 50 200 APoint@8 64 200 16 48 8 Point p1 APoint@64 8Point p2 64 Point p2 = p1; p1 = new APoint(200,200); p2.getX()  100 p1.setX(100); p2.getX()  100 Point p1 = new APoint(50, 50); P1P2 APoint@64APoint@8 p2 = p1;

13. Assignment of Object Variables 100 50 200 APoint@8 64 200 16 48 8 Point p1 APoint@64 64Point p2 64 Point p2 = p1; p1 = new APoint(200,200); p2.getX()  100 p2 = p1; p2.getX()  200 p1.setX(100); p2.getX()  100 Point p1 = new APoint(50, 50); P1P2 APoint@64APoint@8 Garbage collected

14. == for Objects 200 APoint@8 64 200 16 48 8 Point p1 APoint@64 8Point p2 64 Point p2 = new APoint(200, 200) Point p1 = new APoint(200, 200); P1P2 APoint@64APoint@8 p2 == p2  false Same physical object?

15. == for Objects 200 APoint@8 8 16 48 8 Point p1 8Point p2 Point p2 = p1; Point p1 = new APoint(200, 200); p2 == p2  true P1P2 APoint@8

16. == Vs Equal for Strings Joe Doe String@8 64 16 48 8 String s1 String@64 8String s2 64 String s2 = “Joe Doe” String s1 = “Joe Doe”; S1S2 String@64String@8 s1 == s2  false s1.equals(s2)  true

17. == Vs equals() for Objects 200 APoint@8 64 200 16 48 8 Point p1 APoint@64 8Point p2 64 Point p2 = new APoint(200, 200) Point p1 = new APoint(200, 200); p2 == p2  false public boolean equals(Point otherPoint) { return x == otherPoint.getX() && y == otherPoint.getY(); } p1.equals(p2)  true