contoh inheritance di java

class PERSEGI {
protected double panjang, lebar;
public PERSEGI() {
setPL(1,1);
}

public PERSEGI(double p, double l) {
if (p>0 && l>0) {
panjang = p; lebar = l;
} else {
panjang = 2.0; lebar = 1.0;
}
}

public void setPL(double p, double l) {
if (p>0 && l>0) {
panjang = p; lebar = l;
}
}
public double getPanjang() {
return panjang;
}

public double getLebar() {
return lebar;
}

public double hitungLuas() {
return (panjang * lebar);
}

public double hitungKel () {
return (2 * (panjang+lebar));
}
}

class BALOK extends PERSEGI {
private double tinggi;

public BALOK() {
setPL(1,1);
setTinggi(1);
}

public BALOK(double p, double l, double t) {
setPL(p,l);
setTinggi(t);
}

public void setTinggi(double t) {
if (t>0) tinggi = t;
}

public double getTinggi() {
return (tinggi);
}

public double hitungLuas() {
return (super.hitungLuas() * 4.0 +
super.getLebar() * tinggi * 2.0);
}

public double hitungVol() {
return (super.hitungLuas() * tinggi);
}
}

class contoh_inheritance {
public static void main(String[] args) {
PERSEGI X = new PERSEGI(4.5, 3.5);
System.out.println("DESKRIPSI PERSEGI X");
System.out.println("PANJANG : " + X.getPanjang() + " meter");
System.out.println("LEBAR : " + X.getLebar() + " meter");
System.out.println("LUAS : " + X.hitungLuas() + " meter persegi");
System.out.println("KELILING : " + X.hitungKel() + " meter");
System.out.println("");

double p=X.getPanjang(), l=X.getLebar();
BALOK A = new BALOK(p, l, 3.0);

System.out.println("DESKRIPSI BALOK A");
System.out.println("PANJANG : " + A.getPanjang() + " meter");
System.out.println("LEBAR : " + A.getLebar() + " meter");
System.out.println("TINGGI : " + A.getTinggi() + " meter");
System.out.println("LUAS : " + A.hitungLuas() + " meter persegi");
System.out.println("VOLUME : " + A.hitungVol() + " meter kubik");
}
}