konsep dasar pemrograman java abstract class

berikut akan sedikit dijelaskan tentang abstract class pada java.

• Class abstract dideklarasikan dengan kata kunci abtract ditulis sebelum kata kunci class
• Class abstract memiliki menimal satu method abstract
• Subclass dari class abstract harus mengoverride semua method abstract
• Class abstract tidak dapat dibuat instance, yang bisa hanya class concrete

contoh program menggunakan abstract class

Shape .java
————————————-begin————————————-

public abstract class Shape {
private String name;
Shape(String aName) {
name=aName;
}
public String getName() {
return name;
}
public abstract float calculateArea();
}
class Circle extends Shape {
private int radius;
Circle(String aName) {
super(aName);
radius = 3;
}
public float calculateArea() {
float area;
area = (float) (3.14 * radius * radius);
return area;
}
}
class Square extends Shape {
private int side;
Square(String aName) {
super(aName);
side = 3;
}
public float calculateArea() {
int area;
area = side * side;
return area;
}
}
—————————————–end————————–

ShapeTest.java
————————————-begin—————————
public class ShapeTest {
public static void main(String argv[]) {
Circle c = new Circle(“Circle C”);
Square s = new Square(“Square S”);
Triangle t = new Triangle(“Triangle T”);
Shape shapeArray[] = {c, s, t};
for (int i=0; i
System.out.println(“Area dari ” + shapeArray[i].getName()
+ ” is ” + shapeArray[i].calculateArea()+” sq. cm.\n”);
}
}
}
————————————end—————————

Triangle.java
———————————–begin————————
public class Triangle extends Shape{
private int alas,tinggi;
Triangle(String aName) {
super(aName);
alas = 5;
tinggi = 6;
}
@Override
public float calculateArea() {
float area;
area = (float) (0.5 * alas * tinggi);
return area;
}
}
—————————–end———————–

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