© A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to...
-
Upload
edgar-martin -
Category
Documents
-
view
230 -
download
1
Transcript of © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to...
![Page 1: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/1.jpg)
© A+ Computer Science - www.apluscompsci.com
![Page 2: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/2.jpg)
© A+ Computer Science - www.apluscompsci.com
![Page 3: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/3.jpg)
© A+ Computer Science - www.apluscompsci.com
public Triangle(){ setSides(0,0,0);}
Constructors are similar to methods. Constructors set the properties of an object to an initial state.
![Page 4: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/4.jpg)
© A+ Computer Science - www.apluscompsci.com
public Triangle(int a, int b, int c){ setSides(a,b,c);}
Constructors are similar to methods. Constructors set the properties of an object to an initial state.
![Page 5: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/5.jpg)
© A+ Computer Science - www.apluscompsci.com
public void setSides(int a, int b, int c){ setSideA(a); //more of the same }
Modifier methods are methods that change the properties of an object.
![Page 6: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/6.jpg)
© A+ Computer Science - www.apluscompsci.com
public void setSideA(int a){ sideA=a;}
Modifier methods are methods that change the properties of an object.
![Page 7: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/7.jpg)
© A+ Computer Science - www.apluscompsci.com
public int getSideA(){ return sideA;}
Accessor methods are methodsthat retrieve or grant access tothe properties of an object, butdo not make any changes.
![Page 8: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/8.jpg)
© A+ Computer Science - www.apluscompsci.com
public String toString(){ return "" + getSideA() + //more get calls }
Accessor methods are methodsthat retrieve or grant access tothe properties of an object, butdo not make any changes.
![Page 9: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/9.jpg)
© A+ Computer Science - www.apluscompsci.com
All data members should haveprivate access. The publicconstructors, accessor methods,and modifier methods should beused to manipulate the data. All data is tucked away nicelyinside the class.
![Page 10: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/10.jpg)
© A+ Computer Science - www.apluscompsci.com
The public methods give you access to an object’s privatedata / properties.
getIt( )
setIt( )
toString( )
Class/Object
private data /instance variables /properties
![Page 11: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/11.jpg)
© A+ Computer Science - www.apluscompsci.com
![Page 12: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/12.jpg)
© A+ Computer Science - www.apluscompsci.com
![Page 13: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/13.jpg)
© A+ Computer Science - www.apluscompsci.com
In Java, all classes are sub classes of class Object. This adds greater flexibility when writing programs in Java.
Object
String Date
![Page 14: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/14.jpg)
© A+ Computer Science - www.apluscompsci.com
public class Monster extends Object{ public void print( ) { out.println("Monster"); }}
![Page 15: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/15.jpg)
© A+ Computer Science - www.apluscompsci.com
Because all classes are subclasses of Object, all classesstart with the same methods.
.equals( )
.toString( )
. . . . . and more
![Page 16: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/16.jpg)
© A+ Computer Science - www.apluscompsci.com
![Page 17: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/17.jpg)
© A+ Computer Science - www.apluscompsci.com
![Page 18: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/18.jpg)
© A+ Computer Science - www.apluscompsci.com
All members with publicaccess can be accessedinside and outside of the class where they are defined.
![Page 19: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/19.jpg)
© A+ Computer Science - www.apluscompsci.com
All members with privateaccess can only be accessedinside of the class wherethey are defined.
![Page 20: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/20.jpg)
© A+ Computer Science - www.apluscompsci.com
![Page 21: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/21.jpg)
© A+ Computer Science - www.apluscompsci.com
![Page 22: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/22.jpg)
© A+ Computer Science - www.apluscompsci.com
If you do not provide any constructors, Java will provide a default constructor.
![Page 23: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/23.jpg)
© A+ Computer Science - www.apluscompsci.com
![Page 24: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/24.jpg)
© A+ Computer Science - www.apluscompsci.com
![Page 25: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/25.jpg)
© A+ Computer Science - www.apluscompsci.com
The equals() method is used to seeif two objects have the same contents.
String one = "comp";String two = "sci";out.println(one.equals(two));
![Page 26: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/26.jpg)
© A+ Computer Science - www.apluscompsci.com
class Monster{ private int height;
//methods
public boolean equals(Object obj){ Monster other = (Monster)obj; if(getHeight()==other.getHeight()) return true; return false; }
//methods}
//test code in the mainMonster one = new Monster(33);Monster two = new Monster(12);out.println(one.equals(two));
OUTPUTfalse
![Page 27: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/27.jpg)
© A+ Computer Science - www.apluscompsci.com
![Page 28: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/28.jpg)
© A+ Computer Science - www.apluscompsci.com
Overloading occurs when you have morethan one method or constructor with thesame name. Each method or constructormust have a different parameter list.
# of parameters && data types matter
![Page 29: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/29.jpg)
© A+ Computer Science - www.apluscompsci.com
class Monster{ private int height; //default assinged to 0 private double weight; //default assinged to 0
public Monster(){ height=0; weight=0.0; }
public Monster(int ht){ height=ht; weight=0.0; }
public Monster(double wt){ height=0; weight=wt; }
public Monster(int ht, double wt){ height=ht; weight=wt; }}
![Page 30: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/30.jpg)
© A+ Computer Science - www.apluscompsci.com
![Page 31: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/31.jpg)
© A+ Computer Science - www.apluscompsci.com
![Page 32: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/32.jpg)
© A+ Computer Science - www.apluscompsci.com
getX( ) - accessors
setX( ) - modifiers
Monster() - constructors
Monster
toString( ) - accessor
![Page 33: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/33.jpg)
© A+ Computer Science - www.apluscompsci.com
class Monster{ //instance vars / data fields
public Monster(){ //code }
public void setX( params ){ //code }
public int getX(){ //code }
public String toString() { //code }}
![Page 34: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/34.jpg)
© A+ Computer Science - www.apluscompsci.com
class Monster{ // instance variables
public Monster(){ code } public Monster( int ht ) { code } public Monster(int ht, int wt) { code } public Monster(int ht, int wt, int age) { code } //more methods}
![Page 35: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/35.jpg)
© A+ Computer Science - www.apluscompsci.com
Monster m = new Monster();
MONSTERProperties – height – 0 weight - 0 age - 0methods
m
m is a reference variable that refersto a Monster object.
![Page 36: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/36.jpg)
© A+ Computer Science - www.apluscompsci.com
Monster m = new Monster(23);
m is a reference variable that refersto a Monster object.
MONSTERProperties – height – 23 weight – 0 age - 0methods
m
0x234
0x234
![Page 37: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/37.jpg)
© A+ Computer Science - www.apluscompsci.com
Monster m = new Monster(23, 45);
m is a reference variable that refersto a Monster object.
MONSTERProperties – height – 23 weight – 45 age - 0methods
m0x239
0x239
![Page 38: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/38.jpg)
© A+ Computer Science - www.apluscompsci.com
Monster m = new Monster(23, 45, 11);
m is a reference variable that refersto a Monster object.
MONSTERProperties – height – 23 weight – 45 age - 11methods
m0x2B3
0x2B3
![Page 39: © A+ Computer Science - . public Triangle() { setSides(0,0,0); } Constructors are similar to methods. Constructors set the properties.](https://reader036.fdocuments.net/reader036/viewer/2022062408/56649eda5503460f94bea1bc/html5/thumbnails/39.jpg)
© A+ Computer Science - www.apluscompsci.com