Constructors pls explan the code line by line in comments

[vibaviattigala]

class Cube1 {

int length;
int breadth;
int height;
public int getVolume() {
return (length * breadth * height);
}
Cube1() {
length = 10;
breadth = 10;
height = 10;
}
Cube1(int l, int b, int h) {
length = l;
breadth = b;
height = h;
}
public static void main(String[] args) {
Cube1 cubeObj1, cubeObj2;
cubeObj1 = new Cube1();
cubeObj2 = new Cube1(10, 20, 30);

System.out.println("Volume of Cube1 is : " + cubeObj1.getVolume());
System.out.println("Volume of Cube1 is : " + cubeObj2.getVolume());
}
}

what does this line do?
public static void main(String[] args) {
Cube1 cubeObj1, cubeObj2;
cubeObj1 = new Cube1();
cubeObj2 = new Cube1(10, 20, 30);

where is the constructor?

[Fubarable]

class Cube1 {

int length;
int breadth;
int height;
public int getVolume() {
return (length * breadth * height);
}
Cube1() {
length = 10;
breadth = 10;
height = 10;
}
Cube1(int l, int b, int h) {
length = l;
breadth = b;
height = h;
}
public static void main(String[] args) {
Cube1 cubeObj1, cubeObj2;
cubeObj1 = new Cube1();
cubeObj2 = new Cube1(10, 20, 30);

System.out.println("Volume of Cube1 is : " + cubeObj1.getVolume());
System.out.println("Volume of Cube1 is : " + cubeObj2.getVolume());
}
}

i dont know what did in the example pls explain these code line by line in comments //

Please ask a specific question. What in particular do you not understand? If it is the entire code, then your best bet is to start at the beginning of the tutorials and study Java: Java Language Basics